VOLUME- XX SUMMER 1984
The quarterly journal of the Gemological Institute of America EDITORIAL Editor-in-Chief Editor Editor, Gem Trade Lab Notes STAFF Richard T. Liddicoat, Jr. Alice S. Keller C. W. Fryer Associate Editor 1660 Stewart St. Editor, Gemological Abstracts Santa Monica, CA 90404 Peter C. Keller Dona M. Dirlam Telephone: 12131. . 829-2991 Associate Editor Editorial Assistant Editor, Book Reviews D. Vincent Manson Sally A. Thomas Michael Ross Associate Editor Subscriptions Contributing Editor and John Sinkankas Janet M. Fryer, Manager Editor, Gem News Lisa Hebenstreit, Assistant Manager John I. Koivula
PRODUCTION Art Director Production Assistant Production Assistant STAFF Susan Kingsbury Lisa Joko Christine Wilson
EDITORIAL Robert Crowningshield Anthony R. Kampf Kurt Nassau REVIEW BOARD New York, NY Los Angeles, CA Bernardsville, N1 Pete Dunn Robert E. Kane Glenn Nord Washington, DC Los Angeles, CA Los Angeles, CA Dennis Foltz John Koivula Ray Page Santa Monica, CA Santa Monica, CA Santa Monica, CA Chuck Fryer Henry 0. A. Meyer George Rossman Santa Monica, CA West Lafayette, Indiana Pasadena, CA C. S. Hurlbut, Jr. Sallie Morton James E. Shigley Cambridge, MA San lose, CA Santa Monica, CA
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TABLE OF CONTENTS
EDITORIAL 63 The Magic of Pegmatites Richard T. Liddicoat, Ir.
FEATURE 64 Gem-Bearing Pegmatites: A Review ARTICLES James E. Shigley and Anthony R. Kampf Gem Pegmatites of Minas Gerais, Brazil: Exploration, Occurrence, and Aquamarine Deposits Keith Proctor
NOTES 101 The First-Order Red Compensator: An Effective AND NEW Gemological Tool TECHNIQUES John Ilmarii Koivula
REGULAR 106 Gem Trade Lab Notes FEATURES 113 Editorial Forum 114 Gemological Abstracts 121 Gem News 123 Book Reviews
ABOUT THE COVER: Most of the aquamarine on the world gem market has come from the rich pwtites found throughout the northeastern section of the state of Minas Gemis, Brazil. The history of gem exploration and minim in this area in general, and the geology and occurrence of the famous aquamarine deposits in particular, are discussedin the article by Keith Proctor in this issue. The 898-grain aquamarine crystal on the cover, which is 13.8 cm high x 7 cm wide (5%" x 2%"), is from the Pioneer mine in the Te6filo Otoni-Marambaia pegmatite district of Minas Gerais. As is common with most aquamarines, the stones cut from this greenish crystal would be heat treated to remove the yellow component and produce the blue color associated with fine aquamarine. Photo 01984 Harold &> Erica Van Pelt-Photographers, Los Angeles, CA. Crystal courtesy of Keith Proctor, Colorado Springs, CO. Typesetting for Gems & Gemology is by Scientific Composition, Los Angeles, CA. Color separations are by Effective Graphics, Compton, CA. Printing is by Waverly Press, Easton, MD.
'R>1984Gemological Institute of America. All rights reserved. ISSN 0016-626X THE MAGIC OF PEGMATITES
hen one considers that all of the aquamarine and most of the tourma- Wline, topaz, kunzite, morganite, and many other gem materials are found exclusively in pegmatites, it becomes obvious that the gemologist must be aware of and understand the nature of this unusual rock type.
Although pegmatites are not uncommon and are found virtually worldwide, only a small percentage contain worthwhile gem materials. Yet the often superb quality of the gemstones that are found in pegmatites and the fact that they formed under a unique set of conditions conducive to crystal growth has captured the interest of gemologists and geologists for many decades.
The late Richard H. Jahns, a member of the GIA Board of Governors, was a world-recognized authority on pegmatites. In a real sense, this issue of Gems o) Gemology is dedicated to his memory. Dr. Jahns gave wise counsel to the
8 f ; Gemological Institute of America over many years-from the time that he > I was a professor at the California Institute of Technology through his tenure as head of the Earth Sciences group at Pennsylvania State University and, most recently, as dean of Earth Sciences at Stanford University.
The article by James Shigley (who studied under Dr. Jahns) and Anthony Kampf is an excellent compilation of what we currently know about pegmatites. The essentially two-part article by Keith Proctor reviews both the history and exploration of, and actual mining of aquamarine in, one of the most important gem pegmatite regions of the 20th century: Minas Gerais, Brazil.
With these articles, we hope to take you, the reader, from the basics of what a pegmatite is to the fascinating story of what pegmatite gems have meant historically in Brazil and the production of one very important pegmatite gems tone, aquamarine.
Richard T. Liddicoat, Jr.
GEMS & GEMOLOGY Summer 1984 63 GEM-BEARING PEGmTITES : A REVIEW By lames E. Shigley and Anthony R, Kampf
Many of the important gem ~nineralsseen quamarine, tourmaline, topaz, lzunzite, mor- on today's marliet-aquamarine, tourma- A ganite-these are but a few of the gemstones fo~~nd he,and topaz, among others-come from in the remarlzable mineral deposits that geologists call an unzisual type of rock lznown as a pegmatites (figure 1).Of the many different lzinds of roclz pegmatite. Gem-bearing pegmatites are exposed at the earth's surface, pegmatites contain the crystalline igneous rocks that are distin- greatest ab~~ndanceand variety of gem minerals. Pegmatite guished by their large-size crystals, concen- trations of certain chemical elements deposits in various parts of the world have yielded spec- otherwise rare in the earth's crust, and var- tacular crystals of gem tourmaline (figure 2)) topaz (figure ious urjus~~alminerals. l'egmatites are typ- 31, and beryl (figure41, as well as a host of other minerals ically rather small bodies of roc) WHAT IS A PEGMATITE? The famous mineralogist Hafly first used the word pegmatite in the early 1800s to refer to a roclz with a patterned geometric intergrowth of feldspar and quartz (now commonly termed graphic granite). Today it is ap- ABOUT THE AUTHORS plied to any crystalline roclz that is, at least in part, ex- Dr. Shigley is research scientisl in /he Depar/men/ tremely coarse grained. The term pegmatjte, then, of Research, Gemologica/ lns/ilute of America, Santa Mon~ca,California; and Dr. Kampfis curator primarily refers to the texture of a roclz, that is, the size, of gems and minerals, Los Angeles Counly Mu- shape, and arrangement of mineral grains. In practice, it seum of Natural History, Los Angeles, California. can be applied to a wide range of roclzs of igneous or meta- 07984 Gemological lnsti/ule of Amer~ca morphic origin that exhibit large crystals. 64 Gem-Bearing Pegmatites - GEMS & GEMOLOGY Summer 1984 Figure 1. A selection of gemstones of pegmatite origin ranging from 5.87 to 11.25 ct. Minerals shown (from left to right, and from front to baclz) are us follows: tourmuline (elbaite),garnet (spessartine), chrysoberyl; topaz, feldspar (or~hocluse),beryl (morgunite); beryl (aquumarine), tourmaline (elbaite), tourmaline (elbaite); beryl (heliodor),spodumene (kunzite). Photo by Tino Hammid. In reality! the vast majority of pegmatites are the mineral grains in a granite are quite uniform in found to be chemically and mineralogically simi- size and only rarely exceed several millimeters in lar to ordinary granites andl hence! are called diameter. Those in a pegmatite are usually several "granitic1' pegmatites (as opposed to "gabbroicl' centimeters across on average! but they can range pegmatites' lfsyeniticllpegmatites' etc.). Because from millimeters to meters in diameter (figure 5). gem minerals arel for the most part) found only in Typically there is an increase in crystal size from granitic pegmatites! these will be the focal point of the outer margins toward the interior of the the ensuing discussion. pegmatite body. The largest crystals ever found have come Texture. Although pegmatites are commonly from pegmatites (seel for example! Jahns! 1953; thought of as very coarse-grained roclzsf they ac- Rickwood! 1981; Sinkankas' 198 1). Outstanding tually vary considerably in grain size. This varia- examples include a 14-m-long spodumene crystal bility is important in distinguishing pegmatites from the Etta mine in the Black Hills of South from most other crystalline rocks. For example! Dakota and an 18-m-long beryl crystal from a Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 Figure 2. Multicolored crystal of to~~rmaline with albite feldspar and quartz from a pegmatite in Afghanistan (14 x 9 cm), Photo 0 Harold d Erica Van Pelt. Specimen courtesy of David Wilber. pegmatite at Malakialina! Madagascar. The fa- these pegmatites have generally been of limited mous Harding pegmatite in New Mexico contains economicl scientific! or gemologic interest. A spodumene crystals that are 5 m long (figure 6). small percentage of pegmatites! however! contain Unfortunatelyl these and most other giant crystals additional minerals! such as beryl and tourmaline) are not of gem quality. There are! however, excep- which incorporate certain rare elements. This lat- tions: for instance! a 300-lzg transparent gem topaz ter group of granitic pegmatites, which are the from a pegmatite in Minas Gerais, Brazil! is now on source of most gem rough! have been the principal display in the American Museum of Natural His- objects of pegmatite exploration and mining. tory in New York. Establishing the chemical composition of a rock provides important clues regarding its origin! Mineralogy and Chemistry. The minerals that geologic history, and relationships to other rock occur in any rock depend on the rock's overall types. Relatively fine-grained roclzsl such as gran- chemistry and the pressure and temperature con- ites! are easily sampled and analyzed to determine ditions under which it formed. Most granitic overall chemical composition; however, this is not pegmatites are composed of the same minerals generally the case for pegmatites. Their coarse and found in ordinary granites! that isJ feldspars variable grain size) nonuniform distribution of (microclinel plagio~lase)~quartz! micas (musco- minerals! and often poor surface exposure pose vite, biotite)! and on occasion some common ac- serious obstacles to accurate chemical analysis. cessory minerals (table 3; also figure 5). As such Nevertheless! painstalzing work at a number of 66 Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 crystals wjth smolzy quartz from a pegmatite in the Ural Mountains of the Soviet Union (9 cm wide). Photo 0 Harold etl Erica Van Pelt. Specimen courtesy of David Wilber. Figure 4. A superb crydt.01 of morganite beryl with albite feldspar from ;he White Q~~een r~~ine,Pala, California (4 x 5 cm). Photo 0Harold d Erica Vun Pelt. Table 1. Occurrence of gem minerals in pegmatites. m Relative Pegmalites the Mineral abundancea major source? Common Feldspar (gem varieties A no orthoclase, amazonite, moonstone) Quartz (gem varieties rock crystal, amethyst, smoky, rose, citrine) Unusual (containing rare elements such as Li, Be, B, P, F, Cs, etc.) Apatite Amblygonite Beryl (gem varieties aquamarine, morganite, heliodor, goshenite) Beryllonite Brazilianite Figure 5. Small pegmatite body cutting through Chrysoberyl granite at the Fletcher stone quarry near Danburite Westford, Massachusetts. Both the pegmatite and Euclase Garnet (spessartine) enclosing granite are composed of feldspars, Hambergite mica, and qLlartz, but within [he peg~nu~itethe Herderile crystals are m~~chlarger, In addition, the Lepidolite cryslals near the center of the pegmatite are Petalite Phenakite larger ~hanthose along the outer margins. Pollucile Pho~oby Richard H. Iahns. Spodumene (gem varieties kunzile, hiddenite) Topaz Tourmaline (elbaite-gem Common granitic pegmatites show little devi- varieties rubellite, ation from typical granite chemistry (compare achroite, indicolite; liddicoatite) columns 1 and 2 in table 3).In contrast, those that contain small amounts of unusual minerals ex- aRelatiave abundance in granitic pegmafiles: A =abundant and wide- hibit marlzed enrichments in a variety of rare ele- spread; C = common or locally abundant; R = rare or uncommon; VR = very rare. ments (table 3, column 3). Lithium, berylliuml boron, and fluorine, in particular, are essential constituents in several important gem minerals. localities has yielded meaningful estimates of the Despite their small total amounts (seldom over 2 chemical composition of granitic pegmatites (see wt. expressed as oxides), the concentrations of table 3). these and other rare elements in some granitic TABLE 2. Some of the more important gem pegmatite regions. -- -- Region Tourmaline Beryl Spodumene Topaz Quartz Garnet Afghanislanlpakistan Brazil Madagascar Mozambique Namibia Soviet Union Ural Mountains Transbaikalia Ukraine East Africa United States New England Colorado California 68 Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 Figure 6. View of the Haiding pegmatite in Taos County, New Mexico. Several internal zones are visible as colored band's with differing texture and mineral content. This large, complex pegmatite, approximately 80 m thick, is rich in lithium minerals and rare elements, but apparently crystallized at too great a depth in the crust to allow for the formation of gem-bearing pockets. The elongate, ligh t-colored crystals are common spodumene reaching 5 m in length. Photo by Richard H. Jahns. TABLE 3. Chemical and mineralogical comparison of pegmatites can exceed by several orders of magni- granite and granitic pegmatites, tude the amounts found in other rocks. In fact, the mining of pegmatites for rare elements, or even for Component/ Common Gem-bearing phase Granitea pegmatitec the common pegmatite minerals, has at times been of far greater economic importance than the Chemistry mining of pegmatites for gemstones. For instance, Si02 A1203 the Harding pegmatite (figure 6) was an important FeO + ~ei0; wartime source of beryl for beryllium, of lepidolite Ti02 - - and spodumene for lithium, and of microlite for MnO - 0.28 tantalum. "20 0.6 0.39 MgO trace CaO 0.3 1.36 DESCRIPTIVE CLASSIFICATION Na20 4.6 4.45 K20 4.2 2.85 Efforts over the past century to better understand Li20 - 1.49 granitic pegmatites and their distinctive features P2° 0.3 0.07 have led to numerous attempts to classify them F 0.1 0.11 - 0.18 according to some logical framework. Most early B2° Be0 trace trace schemes were descriptive in nature, and were Rb20 + Cs2O - trace based on various observable features such as shape Total 99.86 or key minerals (see Landes, 1933; Jahns, 1955; Mineralogy Vlasov, 1961; Cerny, 1982). One of the most Major phases Microcline Microcline Microcline widely accepted of these descriptive classifica- Quartz Quartz Quartz tions was summarized by Heinrich (1956). This Plagioclase Albite Albite Muscovite Muscovite Muscovite scheme, which is still useful today, divides grani- Biotite tic pegmatites into three types on the basis of in- Minor phases Beryl Beryl ternal structure: Tourmaline Tourmaline Apatite Apatite 1. Simple (figures 5 and 7a)-lack any segre- Garnet Garnet gation of minerals; may or may not display Spodurnene a systematic variation in texture; consist Rhodizite Lepidolite mostly of common silicate minerals with Hambergite accessory minerals on some occasions. Danburite 2. Zoned (figures 7b, 8, and 9)-possess dis- 'Westerly granite, Westerly, Rhode Island (Turtle and Bowen, 1958). tinct internal zones of contrasting mineral ^~iamondMica pegmatite, Keystone, South Dakota (Norton, 1970). cGem-bearingpegmatite, Manjaka, Madagascar (Schneiderhdhn, 1961). content and texture; often larger than the simple types; consist of common silicate Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 Granitic host rock - No internal zones: quartz-microcline-muscovite Wall zone: quartz-plagioclase-microcline-muscovite-biotite Figure 7. Idealized Intermedate zone: microcline-plagioclase-quartz-muscovite diagram showing internal structural relationships in Core zone: quartz simple (a), zoned (b), Core zone: quartz-spodumene complex (c), pegmatites. - Artwork by Christine IGem pockets-secondary replacement minerals Wilson; adapted from Johns (1953). minerals and various accessory species; fieldwork at numerous localities has documented minerals become more coarse grained to- a basic internal arrangement of minerals in ward the interior of the pegmatite. pegrnatites that is generalized in table 4. In the 3. Complex (figures 6 and 7c)-similar to the field, recognition of this mineral arrangement in a zoned types except also exhibit extensive pegmatite is of enormous help both to the student mineral alteration and replacement; often of pegmatites and to the miner (Sinlzankas, 1970). contain high concentrations of rare ele- ments and unusual minerals. GENETIC CLASSIFICATION Simple pegmatites are by far the most numer- Building on the earlier studies, more recent at- ous, while complex pegmatites are the least com- tempts to classify granitic pegmatites have em- mon but of greatest interest to the geologist and phasized the geologic environment of pegmatite miner. Giant crystals, rare elements, and gem formation rather than descriptive details. For ex- minerals are generally restricted to zoned and ample, an alternative scheme proposed by complex pegmatites. Ginzburg et al. ( 1979; summarized in Cernv, 1982) Minerals found in the latter two types of uses the conditions present at various levels in the pegmatites are arranged in layers or zones. As il- earth's crust to help explain observed differences lustrated in figures 8 and 9, in an ideal situation in the nature of pegmatites. They recognized four these shell-like zones are concentrically disposed classes of pegmatites: around an innermost core and tend to follow the 1. Those formed at very great depth (more exterior shape of the pegmatite body. Although the than 11 km), which are generally unzoned internal structure of many zoned pegmatites is and possess little economic mineralization rarely so uniform, and may be quite complicated, other than occasional concentrations of 70 Gem-Bearing Pegmatites GEMS &. GEMOLOGY Summer 1984 Figure 8. View of the Oregon NO. 2% pegmatite in the South Platte pegmatite district, Jefferson County, Colorado. I This zoned granitic pegmatite is a vertical, column-shooed body with an exceptionally well-developed internal arrangement of minerals. The feldspar- rich intermediate zones were removed during mining operations, while the central quartz core was left standing. The pegmatite body is approximately 70m in diameter. Photo by William B. Simmons, /r. uranium, thorium, and rare-earth ele- ments. 2. Those formed at great depth (approximately 7- 11 lzrn), which may be zoned, are gener- ally rich in mica, but have few rare ele- ments. 3. Those formed at intermediate depth (ap- proximately 3.5-7 lzrn), which are often zoked, may contain small crystal-lined pockets, and possess a number of rare ele- ments. 4. Those formed at shallow depth (less than 3.5 lzrn), which are zoned, and which some- times contain rare elements and gem pockets. Ginzburg et al. further contend that at very Granitic host rock great depth pegmatites are formed largely through Wall zone: quartz-microcline-biotite the partial melting or metamorphic recrystalliza- tion of existing roclzs essentially in place, while at Intermediate zone: microcline lesser depths pegmatite formation becomes more 1 Core zone: quartz and more an igneous process involving the injec- I tion of a magma (molten rock) and its subsequent crystallization. Figure 9. Idealized block diagram of a zoned granitic pegmatite similar to the one shown in OCCURRENCE figure 8. Note the horizontal and vertical zone Geologic Setting. Compared to most other rock structure and the apparent outcrop pattern types, pegmatites are relatively rare, yet they are resulting from the different levels of exposure widely scattered in the earth's crust and can be possible. Artwork by Christine Wilson; adapted from Simmons and Heinrich (1980). locally abundant. Pegmatites tend to be most common in particular geologic settings, generally where igneous or metamorphic rocks are exposed matites near Bancroft, Ontario). Those formed at at the earth's surface (Jahns,1955; Schneiderhohn, deep and intermediate depths occur in folded and 1961; terny, 1982). Those pegmatites formed at metamorphosed rocks in mountain belts (e.g., the very great depths are usually found in metamor- mica pegmatites in the Soviet Union, and the phosed roclzs that comprise the ancient cores of beryl-spodumene pegmatites of the Black Hills, continents (e.g., the uranium-rare-earth peg- South Dakota). The shallow-depth pegmatites are Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 71 associated with large, buried masses of intrusive million years ago. As might be expected from their igneous rocks, known as plutons or batholiths, frequent occurrence in mountainous regions, that frequently underlie mountainous areas (e.g., pegmatites can often be correlated in age with the the gem-bearing pegmatites of southern Califor- corresponding orogenic (mountain-building) nia, of the Hindu Rush region of Afghanistan, and periods. of Minas Gerais, Brazil). Pegmatites in each of these depth-of-formation categories gradually be- Size. In general, pegmatites are rather small rock come exposed at the surface over geologic time by bodies, although quite large ones do occur. Out- either erosion or large-scale mountain uplift, and crops of pegmatites have been observed to range thereby become accessible. from centimeters to meters in minimum dimen- sion and up to several kilometers in maximum Genetic Relationships. The close petrologic rela- dimension (e.g., compare figures 5 and 6). Typi- tionship that is sometimes apparent between cally, pegmatite bodies are completely enclosed by pegmatites and plutonic igneous rocks has been other kinds of rocks. The actual dimensions of taken as evidence that most pegmatites them- pegmatites are often difficult to estimate, not only selves result from the crystallization of silicate because they are frequently irregular in shape, but magmas. However, this connection is most obvi- also because very little of the pegmatite is exposed ous for the shallow pegmatites. As depth increases, on the surface. metamorphic processes seem to play a greater role in pegmatite formation. Shape. Pegmatites are among the least regular and most varied in shape of all rock bodies. This wide Age. The ages of pegmatites span much of the diversity can be attributed to a number of factors, geologic time scale from 3.9 billion to less than 100 including the depth of formation, the mechanical TABLE 4. Some generalized features of internally zoned granitic pegmatitesa Mineralogy Zone Thickness Texture (accessory phases) Other comments Border Usually a few centime- Plagioclase-quartz- May or may' not have ters, but sometimes muscovite (garnet, sharp contacts with the thicker tourmaline, other surrounding host rocks phases) Wall Usually on the order of Generally coarser than Plagioclase- May not be continuous several meters border zone microcline-quartz or of uniform thickness (muscovite, beryl, tour- around the entire maline, garnet, other pegmatite phases) Intermediate Each zone may reach Progressively coarser Microcline-quartz- May consist of a number (possibly several meters in thick- grain size proceeding spodumene-amblygonite- of distinct zones of dif- several ness depending on the inward; some giant muscovite-plagio- fering mineralogy; each zones) size and shape of the crystals; inner~riost clase (tourmaline, may or may not com- pegmatite zones may contain phosphate minerals, pletely enclose the some pocket-rich areas beryl, other phases) central core; interme- diate zones contain the giant crystals and comprise the bulk of the pegmatite; unusual minerals often con- centrated toward core Core Up to several meters in Variable-may contain Quartz-spodumene- Core zone may be thickness depending on both coarse- and fine- microcline (tourmaline, composed of several the size and shape of grained material; some lepidolite, beryl, topaz, segments; gem pockets the pegmatite giant crystals; may in- gem minerals, other often located on the clude pocket-rich areas phases) contact between the core and the enclosing intermediate zones aAdapted from Cameron el a/. (1949) and Norton (1983). 72 Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 internally zoned pegmatites, but even here they are infrequent. Although pocket-bearing granitic pegmatites are widespread in such regions as Minas Gerais, Brazil, and southern California, Jahns (1955)suggested that these cavities probably occur in less than one percent of all known pegmatites. Furthermore, few pocket-bearing pegmatites have the rare elements necessary for the formation of gem minerals in high-quality transparent crystals (figure 10). In fact, most con- tain only crystals of the basic constituents of the pegmatite itself, namely quartz, feldspars, micas, and schorl. Even within the same pegmatite body, pockets Figure 10. Portion of an open gem pocket in the can vary greatly in size and shape. Most are less famous Himalaya pegmatite of Mesa Grands, than several centimeters in diameter, but a few California, with multicolored crystals of gem several meters across have been reported. Never- tourmaline up to several centimeters in length theless, the total volume of pockets is usually triv- along with pale crystals of feldspar and quartz. ial in comparison to that of the enclosing Photo by Michael Havstad. pegmatite. There seems to be no particular rela- tionship between the dimensions of the pegmatite and the number, size, or shape of its pockets. Even properties of the host rock at that depth, and the within the same pegmatite region, some tectonic and metamorphic processes that took pegmatites are remarkably rich in pockets (e.g.,the place at the time of formation. Shallow pegmatites Himalaya pegmatite shown in figure 11)) while often fordsheet-like dikes, veins, or lenses that others have few if any. occur along faults or fractures in pre-existing host Pockets are usually found within the central rocks. Deeper pegmatites, on the other hand, tend core or along the margins between the core zone to be elliptical or ovoid as a result of the more and the enclosing intermediate zones. The mineral plastic character of the enclosing rocks at depth. content from one pocket to another, even in a given pegmatite, is likely to vary considerably. OCCURRENCE OF GEMSTONES Figure 12, a diagram of an actual gem pocket Gemstones never constitute more than a small found in a granitic pegmatite in southern Califor- portion of any pegmatite body. Certain of the more nia, illustrates several important characteristics of common gem minerals, such as tourmaline, beryl, gem pockets. Pocket crystals are firmly rooted in and spodumene, can occur as giant crystals in the the surrounding massive pegmatite, but in the intermediate or core zones of pegmatites. How- open space of the pocket they are able to grow ever, such large crystals are almost always highly freely and thereby develop regular crystal faces. fractured and clouded with inclusions, and conse- Crystals of feldspar and quartz are usually larger quently are of little or no gem value. The smaller, and more abundant than those of any gem min- transparent crystals of these and other gem min- erals that may be present. Pocket crystals are often erals are generally found only in pegmatite cavi- distributed nonuniformly, as is the case with the ties, or "pockets." pocket in figure 12, where tourmaline was only Pockets are irregular openings in otherwise found in place on the roof of the cavity. In some solid pegmatite (see figure 10). As found today, instances these crystals are etched or corroded as a these pockets are usually filled partly or complete- result of chemical attack (see figure 13) and may ly with clay, but during pegmatite crystallization exhibit replacement by secondary minerals. Bro- they provided the necessary open space into which ken crystals of feldspar, quartz, tourmaline, and crystals could grow unimpeded, thereby attaining other minerals that once grew from the walls are a very high degree of internal and external perfec- sometimes found scattered about in the pocket, tion. usually embedded in clays that formed after the Pockets are most common in the complex, crystals had finished growing. Few gem species are Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 Figure 1 1. Underground mine view of the Himalaya pegmatite. The pegmatite, only about 1 m thick, is remarkably rich in gem pockets and has been a noted producer of gem tourmaline. Thepegmatite consists of tan and grayish feldspars, grayish quartz, pink lepidolite, and blaclz schorl. The light-colored areas along the central portion of the pegmatite arenewly exposed but still intact gem pockets. Within the pockets, crystals of gem tourmaline are embedded in clays and other secondary alteration minerals. Photo by Michael Havstad. found in any one pocket-in this case tourmaline and project into a pocket. was the only gem mineral present. Miners often use the color changes in tourma- Some gem minerals exhibit compositional zo- line embedded in the massive pegmatite as an in- nation to a varying degree within individual crys- dication that a pocket area may be close by. Other tals. In an extreme example, such as tourmaline, indicators are the presence of lepidolite, the in- this zonation is reflected in color zoning. That is, creased transparency of quartz, the blaclz staining tourmaline crystals may have black, opaque of the pegmatite by manganese oxides, extensive (schorl) roots in the solid pegmatite and become rock alteration, and the presence of clays. Miners pink, green, blue, etc. (elbaite) as they approach quickly learn, however, that each pegmatite is Figure 12. Diagram of a mapped, vertical cross section through a small, tourmaline-bearing gem pocket in the Stewart pegmatite, Pala, California. Crystal fragments of quartz and gem tourmaline, broken during the final stages of pocket formation, are embedded in the pocket-filling clay material. Artwork by Christine Wilson; adapted from Johns (1979). 1 Microcline Feldspar Albite Feldspar 1 Quartz 1 Muscovite Lepidolite I] Pocket clay with numerous small crystal fragments 1 1 Tourmaline 2.5cm Massive Pegmatite surrounding pocket 74 Gem-Bearing Pegmatite8 GEMS & GEMOLOGY Summer 1984 unique, with its own set of pocket indicators. They also learn that, despite careful attention to these clues, the location of productive gem pockets is still largely a matter of luck and hard work. THE GENESIS OF GEM PEGMATITES Although in the past there has been considerable disagreement among geologists regarding the ori- gin of granitic pegmatites, there is a general con- sensus today that at least the shallower ones formed by crystallization from a magma. Numer- ous theories have been proposed to explain the formation of pegmatites via magmatic crystalli- zation (see Landes, 1933; Jahns, 19551, but perhaps the most widely accepted general model is that of Jahns and Burnham (1969; also see Jahns, 1953, 1979, 1982). Their model is based on the work of many early investigators, notably Fersman ( 1931). The key points of this genetic model relevant to internally zoned granitic pegmatites containing gem minerals are described below. Starting Materials. The starting material for a gem-beaii& pegmatite is a volatile- and rare element-!rich silicate magma derived from the final stages of crystallization of certain granitic magmas. 'Water is the most important volatile constituent of this pegmatite magma; however, other volatiles-such as fluorine, boron, lithium, carbon dioxide, and/or phosphorus-may be pres- Figure 13. This crystal of gem green beryl from ent. The rare elements include beryllium, cesium, the Ukraine region of the Soviet Union niobium, tantalum, and tin, among others. Both (9 x 17.5 cm) displays intriguing surface features caused by chemical etching that took place groups of constituents may be present at much subsequent to its formation in a pegmatite gem higher levels in pegmatite magmas than in the pocket. Photo 0 Harold o) Erica Van Pelt. parent granitic magmas. Emplacement and Initial Crystallization. This as feldspars, quartz, and micas. Because of their pegmatite magma is injected into fractured rock in chemical and structural makeup, the early-formed the upper portion of the crust; as the temperature minerals cannot, for the most part, incorporate the falls, the magma begins to crystallize. Mineral volatiles or rare elements present in the magma. formation begins at the outer margin of the As a result, these components are preferentially pegmatite magma chamber at temperatures retained in the magma, where they become pro- somewhat below 1000°CPlagioclase feldspar, gressively concentrated. As crystallization con- quartz, and muscovite mica crystallize first as the tinues with further cooling, the water content of fine-grained border zone. Later, these are joined in the magma eventually reaches a saturation level. the coarser-grained intermediate zones by mi- At this point, an aqueous fluid, rich in volatiles crocline feldspar and additional minerals, such as and certain rare elements, separates from the re- common spodumene and beryl. maining pegmatite magma at between 750 and 650°C Concentration of Volatiles. The major chemical elements of the pegmatite magma determine the Nature of Aqueous Fluid. The physical properties nature of the abundant, first-formed minerals such of this aqueous fluid are markedly different from Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 those of the magma and, therefore, the fluid greatly occurrence of abundant liquid inclusions in many affects the subsequent crystallization of pegmatite pocket crystals (and the gems faceted from them) minerals. The much lower viscosity of the aque- attests to their growth from an aqueous fluid. The ous fluid permits the rapid transport of chemical final temperature for mineral crystallization from nutrients to the growing crystals, thereby promot- this fluid may be as low as 250°C ing their growth in the innermost zones of the pegmatite. Its greater concentration of volatiles Evolution of the Pocket. Unfortunately, the chang- and many of the rare elements contributes to the ing fluid chemistry, coupled with decreasing tem- partitioning of elements between magma and perature and increasing pressure, can eventually fluid, and thereby to the segregation of minerals in lead to the destruction of many pocket crystals. In separate zones. In addition, vertical segregation of addition, earlier-formed minerals may become un- minerals has been attributed to the rise of the stable in contact with this highly reactive fluid. As less-dense fluid within the pegmatite magma a result, some pockets are found to contain only chamber. The aqueous fluid seems, in general, to the remnants of what may have been gem-quality be a superior solvent. Minerals crystallize from it crystals altered to secondary minerals such as at lower temperatures, and can grow to greater lepidolite mica and montmorillonite clay. Most of size, than from the magma. The fluid also tends to those pockets that ultimately produce gem min- redissolve some earlier-formed minerals with erals are thought by some to have undergone a which it comes in contact. This fluid is probably final, very important step. This step involves the responsible for much of the secondary mineral re- leakage of volatile fluids through breaks in the placement observed in complex pegmatites. pocket walls that may have resulted from one or more of a number of possible mechanisms: Intermediate Stages of Crystallization. The 1. Increase in fluid pressure within the pock- volatile-rich, aqueous fluid continues to exsolve ets that eventually exceeds the confining from the magma as crystallization proceeds, and pressure or strength of the surrounding minerals in the inner zones of the pegmatite form massive pegmatite. in the presence of both the fluid and the magma. 2. Cooling and contraction of the pegmatite The last remaining magma eventually disappears body. at temperatures between 600Âand 500°CThe in- nermost portions of the pegmatite are now occu- 3. Earth movements in the vicinity of the pied by large crystals of feldspar and quartz (and pegmatite body. possibly common spodumene or beryl) with a few If the leakage of volatiles is gradual, the pocket isolated, intervening "pockets" of trapped fluid. crystals will remain intact. Unfortunately, evi- dence indicates that the pocket fluid often escapes Formation of Pocket Crystals. The formation of rapidly, resulting in a very sudden drop in pressure minerals in open pockets is the final stage in the and a consequent dramatic decrease in tempera- primary crystallization of the pegmatite. With de- ture. The resultant "thermal shock" is thought to creasing temperature (600' to 400°Cand rising be responsible for much of the internal fracturing internal pressure (resulting from the release of vol- often observed in gem crystals, as well as for the atile~),crystallization continues from the fluid. shattered fragments of crystals found on the floors Euhedral crystals of various minerals are able to of many gem pockets or embedded in the pocket form from the fluid within the open space of the clay. The fluid lost from the pocket is injected into pockets. At this stage, the concentrations of cer- fractures in the surrounding pegmatite where it tain rare elements may reach sufficiently high results in the replacement of earlier-formed levels for the crystallization of corresponding unu- minerals. sual minerals. In some instances, non-gem-quality Depth of formation is an important factor in crystals projecting into the pocket continue to determining whether pocket rupture will occur. It grow and attain a more flawless, gemmy termina- also seems to be a factor in determining whether tion. This continued mineral growth is accompa- pockets will form at all, because pockets are only nied by changes in the chemical composition of found in the shallow and intermediate-depth the fluid which, in turn, are reflected in corre- pegmatites. It has been suggested that the separate, sponding changes in some minerals (i.e., as exem- less dense, aqueous fluid phase, thought to be re- plified by the color zonation of tourmaline). The quired for pocket formation, is only able to exsolve 76 Gem-Bearing Pegmatites GEMS & GEMOLOGY Summer 1984 from the magma under the lower confining pres- matite~.A small percentage of pegmatites contain sures experienced by pegmatites formed at shal- well-formed crystals of gem minerals in pockets in lower depths. This would explain the apparent their interiors. lack of pockets in deeper pegmatites and the ab- With the increased demand for colored gem- sence of pockets altogether from pegmatites in stones, the mining of pegmatites for gem material many parts of the world. will continue to be an activity of small scale but great economic importance. This demand is lead- SUMMARY ing to accelerated exploration of pegmatite regions Pegmatites are among the most geologically inter- for new sources not only in long-established areas esting and gemologically important types of rocks such as Brazil and southern California, but also in exposed at the earth's surface. They are crystalline newly discovered or recently accessible areas such rocks that are often characterized by highly varia- as East Africa, Madagascar, and Afghanistan. ble texture, giant-size crystals, unusual minerals, Gem-bearing pegmatites are most likely to be and concentrations of rare elements. Pegmatites found in geologic environments where the originate from residual magmas derived by partial pegmatite magmas crystallized at shallow crustal melting of crustal rocks or as products of the final depths. Pegmatites that form in other geologic stages of igneous crystallization. Crystallization of settings hold less promise as sources of gemstones these magmas, which are sometimes rich in vola- because physical and chemical conditions in these tiles and rare elements, gives rise to the distinctive instances seem to preclude the formation of open mineral content and textural features of peg- pockets and, therefore, gem crystals. Norton J.J. (1970)Composition of a pegmatite, Keystone, South Dakota. American Mineralogist, Vol. 55, pp. 98 1 - 1002. Cameron E.N., Jahns R.H., McNair A.M., Page L.R. (1949)In- Norton J.J.(1983) Sequence of mineral assemblages in differen- terrial Structure of Granitic Pegmatites. Monograph 2, Eco- tiated granitic pegmatites. Economic Geology, Vol. 78, nomic Geology, Urbana, IL. pp. 854-874. tern$ P., Ed. (1982)Granitic Pegmatites in Science and Indus- Rickwood P.C. (1981) The largest crystals. American Mineral- try. Short Course Handbook, Vol. 8, Mineralogical Associa- ogist, Vol. 66, pp. 885-907. tion of Canada, Winnipeg. SchneiderhOhn H. (1961)Die Erzlagerstiitlen cler Etde. II. Die Fersman A.E. (1931)Les Pegmatites, leur Importance Scien- Pegmatite. Gustav Fischer Verlag, Stuttgart. tifiqiie et Practique. Akademiya Nauk SSSR, Leningrad. Simmons W.B. Jr., Heinrich E.W. (1980)Rare-earth pegmatites Translated from Russian into French under the direction of of the South Platte district, Colorado. Resource Series 11, R. du Trieu cle Terdonck and J. Thoreau, University de Colorado Geological Survey, Denver, CO. Louvain, Louvain, Belgium, 1952. Sinkankas J. (1970)Prospecting, for Gemstones and Minerals. Ginzburg A.I., Timofeyev I.N., Feldman L.G. (1979)Principles Van Nostrand Reinhold, New York, NY. of Geology of Granitic Pegmatites (in Russian). Nedra, Sinkankas J. (1981)Emerald and Other Beryls. Chilton Book Moscow (summarized in Cerny, 1982). Co., Radnor, PA. Heinrich E.W. (1956)Radioactive pegmatite deposits-how to Tuttle O.F., Bowen N.L. (1958)Origin of Granite in Light of know them. Canadian Mining Journal, Vol. 77, No. 4, Experirnental Studies in the System NaAISiiOx-I Gem-Bearing Pegmati tes GEMS & GEMOLOGY Summer 1984 77 GEM PEGmTESOF MINAS GERAIS, BRAZIL: EXPLOWTON, OCCURRENCE, AND AQUWNEDEPOSITS By Keith Proctor The norlheastern porlion of the state of illions of carats of fine gem aquamarine) tourma- Minas Gerais, Brazil, coi~tainsthe world's M linel topazl chrysoberyll and lzunzite have come greatest concentration of complex granitic from northeastern Minas Gerais in this century. Their pegmatites, which are especially noted {or source is the complex series of granitic pegmatites found the production of gem beryl, chrysoberyl, throughout this 233!000 km2 (901000sq. mi.) region. Their topaz, to~~rmaline,and kunzite. Pegmatite gen~stoneswere first found in this region chief producers were the colorful garimpeiros who ex- over 400 years ago; in the last 100 yeors, tracted them from the thousands of diverse deposits in this Brazil has supplied most of the world region. The result is some of the most beautiful gems ever market for these five gemstones. As the to appear in fine jewelry (figure 1). first of a series of articles on this region and This series of articles reviews the most important these gem materials, this article reviews pegmatite deposits in this region for the five types of the early exploration for gemstones, their gemstones mentioned above (figure 2). Because of the occurrence, and the mining ine~hodsand enormous complexity of the area, the author has at- miners responsible for the development of tempted to simplify the discussion by grouping the occur- the deposits. Focus is then given to some of rences into districts. Although the districts are seldom as the major deposits of aquamarine and other beryls, especially in the Tedfilo sharp as indicated on the map in figure 2, they do help Otoni -Marambaia and Jequitinhonha manage this unwieldy subject. River valley districts. The story of the gem pegmatite deposits of Minas Gerais begins over 400 years ago with the first expeditions into the interior of Brazil. This article continues with a discussion of early mining in the areal the geochemistry ABOUT THE AUTHOR and geologic development of the pegmatite deposits! and Mr. Proctor is pres~dentof Keith Proclor Fine Gems, the mining methods used in recent times. Following this a wholesale gem import firm, in Colorado Springs, introductionl the major deposits of aquamarine and other Colorado. beryls are described) including associated minerals! major Acknowledgments: The aulhor [hanks the following people, only some of the many who helped with this specimens produced! geologic occurrencel and production article: for translating, H, Arosleguy, F. Baslos, R, figures where available. Future articles in this series will Downes, R. McCIellan, P, Nelo, J. Uemura; for deal with the major tourmaline) topaz! chrysoberyl, and artwork and typing, Melta Marie Fife and Lyn kunzite deposits in this important region. Moffetl; for reviewing and critiquing the original . manuscript, Drs, P. Bariand, R, Gaines, P, Keller, P. Moore, R. Nash, F. Pough, J, Shigley, and HISTORY, OCCURRENCEl J. S~nkankas;and for their invaluable information and assistance, Dr. C,Barbosa, K. Etawar, H. F. AND MINING Kennedy, A. Lucio, A, Sabbagh, J, Sauer, H. Stern, and A. Tavares. Special appreciation goes lo EARLY EXPLORATION AND MINING Mauna Proclor for her help in translating, typing, Brazil was discovered first by the Spaniard Vincente and editing and for her constant support, Pinyon in 1500 and then by Portuguese navigator Pedro 01984 Gemological lnslilute of America Cabral that same year. Cabral was looking for spices) 78 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 Figure 1. These stones represent the variety of fine aquamarines found throughou~the Mims Gemis pegmatite reg :ion. Th stonein the bl pooch at of the photo is from the famous Marta Rocha crystal; the approximately 35-ct stone 1n the rzng is from the Medina mine. Phoio 0 Harold Erica Van Pelt; precious metals, and a route to the Far East for the Letters written in 1500 by Pero Vaz de Portuguese crown. He found none of these) and one Caminha to King Manoel I made reference to the of his pilots even reported in a letter, "It can be existence of gold and silver in the colony, but saidl we found nothing profitable" (Lucio, 1980). omitted proof of such discoveries (Burns, 1965). For the first 50 years, settlement and develop- Although local Indians wore no ornaments of gold, ment were limited entirely to the coastal areas, they told stories of its existence deep within the where no gold or precious gems were to be found. interior. The Indians did wear "precious stones," ' Within this short time, however, the new colony and when they described a green gemstone com- became a major producer of sugar canel dyes (from monly found inland! the Portuguese greedily as- the Brasil tree), and timber. But the Portuguese sumed that it was emerald. They began to plan crown was not satisfied with this wealth; frus- large expeditions to explore and colonize the inte- trated at not having discovered goldl as the rior (Ball! 1930; Banlz, 1979; Zeitner, 1979; Lucio, Spaniards had in the regions that are now Mexico 1980; Moura, 1981). and Perul they pushed incessantly for the explora- The major barrier to exploration was the range tion of the vast interior territory to the west. of mountains that borders much of the coast of Gem Pegrnatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 79 ret to & Gil aSOL Santa Rita-Olho -c Cruzeiro-Aricanga d'Agua-Lufas FF Fazenda do Funil asR Santa Rosa ~~t,~ FL Fortaleza mSa Sapucaia F Frade-Coronel Murta aT Toca de Onqa G Golconda ~UCUrucum HI Happy Island *Up Urupuca JE Jenipapo Xanda *' J Jonas-Cascalho La Laranjeiras Figure 2. This map of the northeastern portion of group also followed the Jequitinhonha River to the Minas Gerais, Brazil, shows lhe major gem mo~intains of Itacambira. From there the pegmatite depositsin this region. Three of the four bandeirantes proceeded southeast to what is now major aquamarine districts discussed are shl~ded Minas Novasl where theydiscovered sands bearing in blue here (for the broad Governador Valadares gold nuggets (Mo~ira,198 11. Carvalho also brought region, only cities near major deposits are noted). back "Brazilian emeraldsI'' just like the crystals he Twoof the better-defined tourmaline districts had originally seen at P6rto Seguro. are alsoshaded: red for [hedistrict hat has produced many of the rr~ostimportant rubellite deposits; The green stones were shipped to Portugall green for the orle responsible forrnuch of the finest where they were cut and subsequently set in the green and blue tourmaline. Blue topaz, not shown crown of Nossa Senhora da Penha. Only after on the map, was found to occur with tourmaline many years had passed were the "Brazilian emer- in the Limoeiro and Xanda mines. Colorless alds!' identified as green tourmalines (Bastos) topaz, often treated to produce blue, is fo~zndover 1972).Bank (1979)and Sinlzanlzas (1974)point out the entire Te6filo Otoni-Marambaia district. that for over 300 years a number of gemological (Sources: Ferraz, 1929; Freyberg, 1934; treatises continued to use the term Braziljan em- Calmbach, 1938; Sinkankas, 1974, 1981; and erald for green tourmaline. ,field investigations of the author,) A third expeditionl led by Fernandez Tourinho) departed in 1571 and traveled by way of the Doce River until they passed the site of the Brazilj it was so heavily forested that passage was almost impossible. The area now called Minas Gerais (General Mines) could only be entered via Fig~zre3. The routes taken by the four rnajor the valleys of the six major rivers that drained the bandeirantegroups that entered what is now the region. Pptuguese pioneers made four large expe- state of Minas Gerais in search of gemstones and precious metals between 1554 and 7674. ditions ufi.these river valleys in the years 1554) 1568) 1571~and 1674 (see figure 31. The iirst expedition was led by Francisco Spinoza. His bandeirante group) so-called because of the banners the men carried on their horses! toolz a torturous route following the Jequitinhonha River to the region where the cities of Serro and Diamantina exist today (Ca16gerasl 1904; Abreu) 1937! 1965; Sousa! 1943; Paiva! 1946). No emeralds or gold were found during this grueling three-year! 11800-kmexpedition) but it is highly lilzely that Spinozals men brought back the worldls first recorded gem tourmaline (Ball) 1930). In his book De Rerum Fossilium, published in 1565' Conrad Gesner provided a quaint woodcut of an elongated! striated crystal with a pointed ter- mination which he called "Smaragdus Bresilicus cylindri specie1' (''A cylindrical species of Brazilian emerald1').The appearance and description of this striated crystal indicate that in fact it was tourma- line (Sinlzankasl 1974) 1981). The second expedition (1568) was commanded by the explorer Martim de Carvalho after he was tempted by some "green stones1'brought to P6rto Seguro-the earliest seaport-by the Indians from the interior (Bastost 1972) 1981; Moura) 1981). These were thought to be emeralds) like those "Emerald reported from Colombia. Carvalhols bandeirante Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Su~nmer1984 81 present-day gem center Governador Valadares. decided to talze advantage of the free land. It is no They then proceeded to the headwaters of the accident that many years later! when the first min- Sua~uiGrande River! passing through the region of ing would be done in alluvial depositsl these ham- the future Cruzeiro and Golconda tourmaline lets became the major gemstone mining centers. mines. Turning northl the bandeirantes traversed Two additional events produced..waves of immi- three river valleys and entered the richest gration that greatly accelerated exploration for pegmatite repon in Brazil! near the present town gemstone deposits: the discoveries of gold near of Ara~uai.They returned to the coast via the Our0 Preto in 1669 and of diamonds near Ara~uai Jequitinhonha River! but not before discovering in 1721 (Sinlzanl~as~1974). green and blue tourmaline and blue beryl crystals! Paes Lemels discovery of gem-bearing which they incorrectly identified as emerald! sap- pegmatites in 1676 was virtually ignored for al- phire! and turquoisel respectively (Eschwege! most 200 years because there was no significant 1833; Moura! 1981). marlzet for Brazilian pegmatite gemstones. At the In the early history of Brazilian mining! most beginning of the 19th century! however! aquama- gems were discovered during the process of testing rine and topaz were mined from near Our0 Preto; alluvial (placer) gravels for gold! and Paiva (1946) and in 18 11, the first large aquamarine on record! a gives Tourinho credit for being the first to find grass-green crystal weighing approximately 7 lzg precious stones by this method. (15 lbs.) was found in the headwaters of the S3o A hundred years passed before the fourth and Mateus River near Te6filo Otoni (Oalzenfulll 1913; most famous of the bandeirante expeditions was Calmbachl 1938; Moura) 198 1).In Europe! much organized and led by Fern30 Dias Paes Leme to interest was aroused in Brazilian gems by London search for the fabled "land of emeralds.'! In a jour- jeweler! lapidary! and mineralogist John Mawe! ney that began in Siio Paulo in 1674 and lasted when he described a great variety of gemstones he almost seven years! he and his band of adventurers had encountered during his travels in Brazil and finally stumbled onto the famous "Emerald offered to supply them on a regular basis (Mawe! Mountains1' (Banlz! 1979; Luciol 1980). 1812). In the immediate vicinity of today's famous Cruzeiro mine and the village of Siio Jose da Safira MODERN DEVELOPMENTS (misnamed llsapphirell for the blue tourmaline The lzey factor in the modern development of found there)! Paes Leme discovered the first re- gemstone mining in Brazil! however! was the col- corded pegmatite-a mountain of mica with the onization of large areas of southern Brazil by Euro- green crystals of his dreams. Soon after his discov- pean immigrants starting around 1850. In particu- ery! however! he was talzen ill with malaria and lar! many German families settled in the Te6filo died. Although he never found true emeralds- Otoni area between 1860 and 1900. again! the green crystals were tourmalines-it is When shiny! transparent! colored crystals ironic that Itabira! one of the hamlets his roving began to appear in the burrow excavations of ar- band settled! later became an important center of madillos and as a result of almost any lzind of emerald production in Brazil (Lucio! 1980). digging activity! the gem-conscious German im- A total of 128 gems (about 430 g)! including migrants immediately recognized the potential llemeraldlllaquamarine! and topazl found during and sent some of the stones to the lapidary center the expedition were shipped to Lisbon in 1682 of Idar-Oberstein for examination. Thus was (Paiva! 1946; Moura! 1981). In 1698 another ship- forged a close relationship between Brazil and ment of stones was sent to Portugal; and these Germany with respect to gemstone mining and stones! when examined by experts familiar with marlzeting that was to last for many decades to emeralds from India! were pronounced "worthless come (Rolff! 1968; Lucio! 1980; R. Nashl pers. tourmaline1' (Bastos, 1972; Banlz! 1979). comm.). These bandeirante expeditions! the longest of From the early 1900s onwards! Lebanese im- which lasted almost seven years and traversed a migrants also established themselves in Te6filo staggering 101000lzm (6!250 mi.)! were responsible Otoni! and the natural association of their tradi- for opening Brazil's enormous interior. Innumer- tional commercial slzills with the industriousness able hamlets along the river valleys were settled by of the Germans led to an enduring relationship. expedition members who tired of the march and During the formative years of the Minas Gerais 82 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 gem trade, the only foreign buyers were the Ger- large wooden crate with its treasure would be mans and one of the first local export firms was shipped directly to Idar-Oberstein. Upon reaching that of Abel Jacinto Ganem. Idar a few days later, however, he was shocked to As early as 1902, a regular system of trading find that the crystal had not yet arrived. He back- was established between Te6filo Otoni and Ger- tracked to Hamburg and found the crate, uniden- many, with the rough being shipped via the newly tified, sitting in the corner of a freight warehouse completed railroad to Caravelas on the coast of the waiting for a claimant. This time he personally state of Bahia. Within a few years, German dealers escorted the crystal to Idar-Oberstein, where the began to make the arduous trek to the small ham- firm Bohrer-Borges took possession and offered it let of Te6filo Otoni. In 1907, Abel Jacinto Ganem for sale for the equivalent of US$139,000. When no and his partner, Feliciano Bamberg, established an museum or other institution stepped forward to office in Idar-Oberstein. buy the crystal in its entirety, it was cut up and the The first garimpos (a series of mining pits, or pieces sold individually (Hahn, 1955; Sinkankas, catras; a garimpeiro is a miner) were started 1981).The American Museum of Natural History around 1900, about 83 lzm north of Te6filo Otoni in New York City now displays the nearly 6-kg in the Marambaia valley, which was known to be a remnant (presumably the only uncut piece of the plentiful source of aquamarine (Lucio, 1980). In Papamel aquamarine) in the J. P. Morgan gem col- late June 1910, a major gemstone discovery was lection (Gaines, 1976; Anderson, 1978; photo in made that was to have a profound and lasting effect Sauer, 1982, p. 30).It is interesting to note that the on the development of gem mining in Minas Papamel aquamarine is the first crystal on record Gerais. The largest and most famous gem aqua- to have been heat treated to obtain its optimum marine crystal found in this century, weighing blue color (Bank, 1973). The current wholesale 110.5 kg (244 lbs.) was unearthed at, the Papamel value of this has been estimated at close to mine on'.the Marambaia River, approximately 20 US$25 million (1. Sauer, pers. comm.) km east ofthe village of Ponto de Marambaia. This News of the selling and asking prices for the abraded and waterworn, doubly terminated, hex- Papamel crystal precipitated a sudden flurry of ac- agonal prism measured 48.5 cm long x 38 cm in tivity by Brazilian miners and German dealers diameter (19 x 15 in.).The major portion was a fine alike. This enthusiasm stimulated the search for blue-green. The crystal was flawless and so trans- aquamarine and eventually contributed to the de- parent that one could read print through it from velopment of the entire central and northern por- end to end (Sinkanlzas, 1974, 1981). tions of the Minas Gerais pegmatite region. The crystal was discovered by the Syrian Aquamarine was popular in Europe even as Tanuri brothers, less than one meter below the early as 1910; the popularization of tourmaline bottom of a colluvial-alluvial pit that had just been came somewhat later, with the development of abandoned in disgust by another miner (Dreher, gemstone mining around the hamlets of ! 1912; Sinkanlzas, 1981). They sold it to two Ger- Governador Valadares and Aracuaf. At this time, man gem dealers, August Klein and Viktor German dealers could reach Governador Vala- Bohrer-Borges, who happened to be in the area. dares, 145 km south of Te6filo Otoni, only by George Kunz (1911) reported the purchase price as horseback along a narrow path cut in the jungle equivalent to US$25,000 and accurately estimated [Lucio, 1980; Caplan and Wilson, 1980). that the crystal would produce 200,000 ct of fin- In 1914, the deposit of green and blue tourma- ished gems. August Klein then undertook a 20-day line first discovered by Paes Leme in 1676 at Serra struggle to transport the massive crystal to the Resplandecente, near the present-day Cruzeiro coast, hauling it first by mule 72 km through the mine, was rediscovered and mining was begun. jungle to the village of Aracuaf, and then floating it Magnificent crystals were produced and used for by canoe down both the Aracuaf and cutting (Lucio, 1980). Jequitinhonha rivers to the coast. From there it In the early 1930s, a garimpeiro named Barbosa traveled via coastal steamer to the city of Bahia discovered spectacular four- and five-color gem (now Salvador), at which point a German steamer tourmalines at the Cascalho mine on the slopes of carried it to Germany (Hahn, 1955; Sinkanlzas, the Itatiaia mountain range near the town of Con- 1981). selheiro Pena. These tourmalines, called After reaching Hamburg, Klein assumed the papagaios (parrots) because of their brilliant Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 83 colors, contributed greatly to the increased a general discussion of the formation of gem demand for tourmaline in Europe (R. de pegmatites. It is important to note again that al- Vasconcelos and H. Bank, pers. comm.). though granitic pegmatites are extremely numer- World War I1 provided the greatest stimulus to ous worldwide, only a small percentage are gem pegmatite exploration in Brazil. Beryl, mica, bearing. Yet literally thousands of gem-bearing feldspar, quartz, and lithium minerals-mostly pegmatites are found in Minas Gerais. The granitic pegmatitic in origin-were needed in great quan- magmas responsible for the formation of these de- tities (OfLeary, 1970; Sinlzanlzas, 1974, 198 1 posits were not only rich in the more common Lucio, 1980).By 1950, the search for these strategic components of silicon, aluminum, iron, mag- minerals had resulted in the discovery of several nesium, potassium, sodium, and calcium, but also hundred gemstone mines (Gonsalves, 1949; Pec- in the volatiles such as fluorine and chlorine, as oral 19501, and this set the stage for the enormous well as such rarer elements as boron, lithium, be- increase in interest in Brazilian gems that followed ryllium, manganese, tin, niobium, tantalum, the war. The city of Governador Valadares, the phosphorus, and the radioactive elements ura- commercial hub for strategic minerals in the area, nium and thorium (Cameron et al., 1949; Pough, became second only to Te6filo Otoni as a 1969; Moore, 1973; Jahns, 1982). The availability gemstone center. of this diverse group of chemical elements resulted A major impetus to the development of these in the formation of thousands of gem pegmatite gemstone mines was that the sale of strategic min- deposits in all stages of mineralogical complexity erals provided a basic income for the mine owners and containing virtually every gem pegmatite while the sale of gemstones provided a margin of mineral species known (Sinkanlzas, 1974, 1981; profitability. For example, some gemstone mines Anderson, 1978). In most cases in Minas Gerais, in the Governador Valadares area pay for their en- the gem materials originated in pockets within the tire operation just with sales of mica and feldspar. host pegmatite. Another vital source of income for gemstone The events that carved the present landscape miners developed starting in the late 1950s, when of Minas Gerais had their beginning so long ago thousands of mineral collectors worldwide began that it is estimated that the surface geology we see buying rare gem crystals and even competed with today was actually formed at some depth (atleast 3 museums for the best specimens (Sinlzanlzas, 1974, lzm [2 mi.] beneath the original surface before ero- 1981; Caplan and Wilson, 1980; Lucio, 1980).The sion took its toll). The pegmatites themselves are sale of natural gem crystals and other rare estimated to be approximately 490 million years pegmatite minerals kept many a mine operating old (Dirac and Ebert, 1967; Cassedanne and Low- during hard times. For example, the Jonas mine ell, 1982).During this period, the older, or "base- recently operated for 18 months on the money ment," metamorphic rocks-schists, gneisses, and generated from the sale of tourmaline specimens. some quartzites-which covered much of the area, acted as a "roof" capping the upward movement of GEOLOGIC DEVELOPMENT OF the molten granitic magmas. However, as the THE PEGMATITE DEPOSITS magmas pushed upward, the overlying basement The pegmatite region of the state of Minas Gerais rocks were fractured and the cooling pegmatitic is undoubtedly the finest laboratory in the world magmas were injected into the systems of cracks, for the study of pegmatite gemology, because it commonly in an approximate north-south direc- contains the world's largest and richest concen- tion (Bassett, 1967; Lucio, 1980). This material tration of gem-bearing pegmatite deposits. Extend- eventually solidified into the primary pegmatite ing approximately 320 kin east to west and 720 lzm deposit, in which the pegmatite body is still en- north to south, it is limited to the eastern and closed in the original schistose or gneissic host northeastern parts of the state (again, see figure 2). roclzs. Depending on local erosion and weathering, These deposits were created by a unique combina- as explained below, such deposits exist today in tion of geochemical, climatic, and other events various stages of decomposition. that are briefly summarized below. During the same geologic time period, large masses of granitic magma also intruded the frac- Formation of the Pegmatites. The reader is referred tured metamorphic rocks vertically and eventu- to the article by Shigley and Kampf in this issue for ally solidified as rounded or hump-like forms. 84 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 ----- / - - .Old Surface ,0 .. #. #. ,^' . ' " ,< . Old vein weathered away and present surface *^;' s. residual gravels and clays now of Hill1 form the Eluvial Deposit ELUVIAL DEPOSIT (Secondary) Found on the top of a hill. as the hill eroded away, the altered decomposed gem pocket COLLUVIAL DEPOSIT "spills" (Secondary) settled only vertically Decomposed dispersed gem pockets which have moved both vertically and laterally down slope as PEGMATITE DIKE hillside eroded away These deposits may or may not - still be associated with primary pegmatite Gemstones still in place ("in situ") in the surrounding host rock. These deoosits exist in Figure 4. Diagram ofprimary various degrees of decomposition '*oh (pegmatite dike) and secondary (eluvial, colluvial, They were subsequently exposed by erosion to A distinctive feature of this entire region is the form the peculiar domed hills and mountains deep chemical weathering of the pegmatite bodies known by the German word inselbergs (island brought about by the soil conditions and the mountains) that are common in many parts of monsoon-like rains that make mining all but im- Brazil (the'mountain known as "Sugar Loaf," in possible from October through February. In many Rio de ~adeiroharbor, is a perfect example). Hun- hillside deposits, the pegmatites are commonly dreds of these tall, deeply grooved, forest-topped altered and decomposed to depths of 50 m or more. batholiths, commonly found in the immediate Since pegmatite bodies are generally not large, fre- vicinity of gem pegmatite deposits, are the most quently the weathered zone extends far beneath prominent physiographic features of the pegmatite the pegmatite itself (Bassett, 1967; Sinkanlzas, region of Minas Gerais. These domes represent the 1974; Lucio, 1980). The contents of gem pockets hardened "backbones" of the granite intrusions, are also chemically altered, with some of their and their presence today is evidence that most of constituents being broken down into secondary the metamorphic "capping rocks" have long since alteration minerals such as clays (Jahns, 1982). eroded away (Dana, 1959; Rolff, 1968; Pough, Generally, only the gem minerals survive; even 1969; Jahns, 1982). the feldspar crystals eventually succumb to the i attacks of water, air, carbon dioxide (carbonic Formation of Secondary Deposits. Weathering. As acid), and soil (humic)acids, and alter to crumbly a result of extensive uplift and the erosion typical white clays principally composed of kaolin. The of a tropical climate and monsoonal conditions, more resistant minerals, such as quartz, beryl, the once-buried schists and gneisses, studded with tourmaline, and topaz, survive and are found in- pegmatite dikes, eventually became exposed on tact in the "softened" decomposed pocket. the surface as "hills," hundreds of meters higher Miners consider the white kaolin a sign that than their present level. Subsequently, this "new" they may be close to gem-bearing pockets. An- surface was again subjected to erosion; the exposed other indication is the occurrence of pocket resi- pegmatites weathered away along with the rest of dues such as fine muscovite mica flakes in the soil the hill and shed their treasures on its slopes. The and, better still, clear or smoky quartz crystals sands, clays, gravels, and loose gemstones now with sharp faces. Once they reach such an altered found blanketing the valley floors, and the red deposit, they look for scattered and detached gem lateritic (clay-like)soil found on the slopes, are the crystals lying loose in the clay. residues of hillside erosion and contain the de- composed and dispersed contents of pegmatites Types of Secondary Deposits, In Minas Gerais, (Sinkanlzas, 1964, 1974). then, gemstones are found not just in pockets in Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 85 the primary pegmatite deposit but also (and more and its host rock (schist or gneiss) still unaltered, commonly) in one of three types of secondary bulldozers, explosives, drills, and other types of deposits-eluvial, colluvial, and alluvial (figure 4). heavy equipment are required to mine the The secondary deposits are those that result from gemstones (figure 5). These deposits are often the the complete decay of a gem-bearing pegmatite richest and most productive (e.g., the Jonas mine) body with consequent release of its resistant min- because their contents have not yet been altered or erals into the soil. In these three types of secondary dispersed. The government grants mining conces- deposits, gemstones have all traveled some dis- sions (registered claims) for such operations be- tance from their original pegmatite. Eluvial de- cause of the great expense involved; today there posits commonly occur on hilltops; as the hill is are only a few-perhaps 30-of these concessions eroded, the decomposed pocket material moved in Minas Gerais (Lucio, 1980). directly downward from the original pegmatite. For the most part, the hard-rock mining Colluvial deposits are pegmatite materials that methods used in Minas Gerais are simple. Miners moved both downward from and lateral to the drill, place dynamite charges, blast, and then clear pegmatite as the pegmatite and its enclosing rocks away the rubble by hand or with some type of earth eroded; a colluvial deposit may or may not be mover. However, even in such mechanized opera- closely associated with its parent pegmatite. tions, the miners still resort to hand sorting when Sometimes the poclzet material is found as a they reach the gem-bearing pockets. 'spill" of gem crystals in the red lateritic soil below the pegmatite outcrop. A textbook example Soft-Rock Mining (Secondary Deposits). Histori- of this deposit type is the Frade aquamarine mine cally, most of the mining of pegmatite minerals near Coronel Murta, discussed later in this article; has taken place in the altered and dispersed sec- in this case, the resistant pocket crystals are still ondary deposits that occur by the thousands in closely associated with the parent body. Lastly Minas Gerais. Because of the softness of the earth there are the alluvial deposits, which are always and the fact that the rock has decomposed, only found in the valley floors and which contain the most basic tools-pick, shovel, and sorting rounded, waterworn stones and gemstones that basket-are needed to free the gemstones (figure represent gravels of a former or still-existing 6). Many of the pits were started even before the riverbed. The condition of the gem material itself turn of the century, when the garimpeiros, or usually reflects the distance it has traveled from miners, could not make a living in agriculture or the original pegmatite. Those specimens found other pursuits. The garimpeiro, usually alone and closer to the primary source have sharper crystal almost always independent, has been a major faces and are less damaged than those found farther factor in Brazil's preeminence as a gemstone pro- away (i.e., crystals found in the pocket itself are ducer for close to 100 years. usually sharper than those found in the eluvial or colluvial deposits, which in turn are less damaged THE GARIMPEIRO: KEY TO THE PAST, than those found in the alluvium). Interestingly, QUESTION MARK FOR THE FUTURE however, although gemstones found in the allu- By federal law, the mineral deposits belong to the vium are usually smaller and more rounded, the government, and any licensed garimpeiro may material itself is much cleaner, since flawed crys- work unprohibited on any state-owned lands tals erode more easily (see the discussion of the where gems and minerals have been found (and Tr6s Barras aquamarine deposits later in this arti- alsoon many private lands, with the prior consent cle). The exception to this general rule is seen in of the owner). The only exceptions are the regis- the Frade aquamarine mine, where even crystals tered claims granted as concessions. However, the found in the primary pegmatite are highly frac- garimpeiro must pay a 10-50% commission to the tured. This is apparently the result of decompres- landowner on all gemstones found, with the exact sion explosion and consequent thermal shock dur- amount determined by how much equipment and ing late-stage pocket formation (see Shigley and food, if any, the landowner gives the garimpeiro as Kampf, 1984). his "grub~talze.~~Only occasionally is the land- owner compensated for the damage done to his MINING METHODS property. Hard-Rock Mining (Primary Deposits). When a The garimpeiro labor force is largely landless, primary deposit is discovered with the pegmatite rootless, and illiterate, but also free and independ- 86 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 Figure 5. ee~vymachinery is often required for hard-rock mining in j :il. / 'rolconda tourmaline mine, bulldozers are used to move the overburden and waste from in^ mine, =ante. . I. ent and ready to move whenever a "bigger" bo- Figure 6, Pick andsl~ovelare the basic tools of the nanza beckons from over the next hillside. At the garimpeiro searching for aquamarine crystals in earliest word of a new, more promising find, often the "soft rock" of this colluvial pit near the a veritable army of garimpeiros-many with their bottom of Frade valley. entire families-will pick up and leave. At each new area, the garimpeiro stakes out a few square meters of land for his private pit, his rights pro- tected by an unwritten but rarely broken code. Large, sprawling temporary villages of shanties lacking utilities or sanitation have been known to spring up overnight. Since 1970, however, several events have combined to make the garimpeiro almost an en- dangered species. During the past 15 years, about 90% of the garimpeiro mining force has left pegmatite mining to obtain steady employment in industry, agriculture, and gold mining. Because of the lack of coal in Brazil and the high cost of its importation, steel companies around Itabira have been forced to buy land and plant millions of fast-growing eucalyptus trees, eventually to be burned into charcoal for use as a reducing agent for iron ore in the production of steel. Both the reforestation projects and the burn- ing of the wood into charcoal are labor-intensive pursuits and now employ thousands of former or potential garimpeiros (Lucio, 1980). Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 most easily accessible secondary deposits dictates that in the future the great majority of gemstone mining in Minas Gerais will have to be done on primary pegmatites using more expensive mech- anized means (Sinlzankas, 1974, 1981; Lucio, 1980). To produce any kind of volume, even the mining of "softened" secondary deposits will re- quire mechanization. This situation suggests that fewer gems will be produced-at even greater pro- duction costs. The unique history and geology of the gem pegmatite region of Minas Gerais forms the basis for the discussion of specific beryl, chrysoberyl, topaz, tourmaline, and lzunzite deposits that fol- low. The beryl (primarily aquamarine) deposits of northeast Minas Gerais are the focus of the next section presented here; the other gem materials will be covered in future articles. AQUAMARINE AND OTHER BERYLS Figure 7. This 40-ct faceted aquamarinesitting on the 898-g "Pioneer" aquamarine crystal Virtually all varieties of gem beryl are found in represents the color that would result if the Minas Gerais, and all except emerald are of natural crystal were cut and the stones heat pegmatitic origin. While heliodor (yellow or treated, the standard practice with aquamarine golden beryl) and morganite (the pink variety) are worldwide. Photo 0 Harold d Erica Van Pelt. found in small quantities in some localities, by far the most important pegmatitic beryl in Minas Gerais is aquamarine. Since the discovery of the In addition, government-financed coffee plan- Papamel crystal in 1910, several other major crys- tations have sprung up all over the region. By 1980, tals and millions of carats of fine aquamarine have 28 million coffee trees had been planted in the been mined from the thousands of deposits that Te6filo Otoni region alone, providing jobs for six to dot the region. eight thousand former garimpeiros. Also, land Four districts in Minas Gerais have produced under plantations or in reforestation projects is major amounts of aquamarine: (1) Te6filo lost to gem mining. The entire hillside known as Otoni-Marambaia, (2) Jequitinhonha River val- the Lavra Jose de Sousa (lavra means workings), at ley, (3) Aracuaf River-Capelinha-Malacacheta, the famed Tres Barras aquamarine deposit, is now and (4) Governador Valadares (see figure 2). covered with coffee trees (Lucio, 1980; Sauer, The following discussion will examine the 1982). important aquamarine deposits in the first two Lastly, gold mining offers a more certain areas, many of which the author visited in 1983, in source of income. Thousands of garimpeiros have terms of their location and access, history and pro- been lured away to work at just one gold mine, the duction, and the important mines and major Serra Pelada, in the northern state of Para; 45,000 specimens found there. Please keep in mind while miners work in a single huge pit. This, and other, reading the discussion and viewing the accompa- gold-mining ventures are likely to go on for dec- nying photographs that most aquamarine has a ades (C. Barbosa and R. Nash, pers. comm.) strong yellow component and thus appears green All of these events have given the descendants when viewed right out of the mine. It is generally of the gem-mining garimpeiros a whole new set of heat treated to remove this yellow component to job options. Many have chosen the security of a produce its optimum blue color (figure 7). Virtu- steady wage rather than the uncertainty of the ally all aquamarine is heated in this manner, the garimpos their parents mined. process duplicates one that commonly occurs in The labor shortage and the depletion of the nature and the resulting color is stable. Depending 88 Gem Pegmatites of Minas Gerais GEMS &. GEMOLOGY Summer 1984 on the mine the crystals come from and the clarity traveling on highway BR-116 north toward of the rough, finished stones are heat treated to Itaobim. Although scattered aquamarine deposits between approximately 250° and 720° for a exist farther south near Te6filo Otoni at Ataleia varying length of time (e.g., a stone with some and Itambacuri-and extensively along the inclusions will be heated at a lower temperature Mucuri, Urucu, and Mateus rivers-the great pre- for a greater number of hours). Less than 5% of the ponderance of pegmatite deposits in this district is aquamarines produced in this region yield top- concentrated in an oval area encompassing a reg- quality, dark blue stones (figure 8). ion roughly 50 lzm north, south, and west of the This section will also review the production of village of Catugi and extending east beyond the heliodor and inorganite in this area. While large village of Cris6lita to include the Pampa River amounts of emerald have been mined in Minas valley (see figure 2). Gerais, they will not be discussed here because This region, dominated by relatively quartz- most deposits are not found in association with poor, coarse-grained gneisses, is perhaps geochem- pegmatites. ically the most distinct pegmatite district in all of Minas Gerais. There are no schists. The pegmatite TEOFILO OTONI-MARAMBAIA magmas in this district were rich in silicon, beryl- PEGMATITE DISTRICT lium, aluminum, fluorine, and boron. All varieties The Te6filo Otoni-Marambaia pegmatite district of beryl except morganite are found here, as are is now easily accessible from Te6filo Otoni by relatively large deposits of chrysoberyl and alexandrite. Cassiterite and columbite also occur. Topaz and aquamarine often occur in the same Figure 8. These aquamarines from the Mucuri pegmatite deposit, but never in the same pocket. In River region (within the Ta6filo Otoni-Marambaia secondary deposits, of course, beryl and topaz are pegmatite 'district) represent some of thybest often found together. color in Minas Gerais. The stones range in weight from 18 to35 ct. Photo 0 Harold o)Erica Black tourmaline is common in this region, Van Pelt; courtesy of lules Saner (Saver, 1982). but there are no lithium minerals, no colored tourmalines, and no known occurrences of mor- ganite. Smoky quartz, citrine, and noncommercial amethyst are also common. This district is noted particularly for the size of the aquamarines found there and the cut stones produced (probably the largest is the 91 1-ct stone in the Smithsonian Institution, Washington, D.C., illustrated on p. 90 of Desautels, 1970).The most important aquamarine finds in this district have been principally in secondary (eluvial, colluvial, and alluvial) deposits in three major areas: the TopAzio - Pavao - Cris6lita valleys, source of the 34.7-kg (76-lb.)Marta Rocha crystal; the Maram- baia valley, where the Papamel aquamarine was found early in this century and then the 22-kg (48-lb.)Quarto Centenario in 1964; and the Tr6s Barras valley, origin of the 19.2-kg (42-lb.)Estrela de Alva (Dawn Star) crystal. Topdzio-Pavao-Cris6lita Valleys. The valleys and basins surrounding the three villages TopAzio, Pavao, and Cris6lita are easily accessible via high- ways BR-116 and MG-409 (see figure 2). These basins are part of the watershed of the Mucuri, Preto, Negro, and Pampa rivers. The abundance of aquamarine in this area led to the sinking of tens of Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 89 thousands of pits in secondary deposits and many earth and abandoned pits. Sauer (pers. comm.) es- tunnels in primary pegmatites since prospecting timated that six million man-hours were wasted was first begun in 1908 (Sinkankas, 1981).These by the garimpeiros over the next 12 months, and have consistently produced large quantities of aq- not one additional aquamarine was found. uamarine. In fact, one of the most important aq- uamarines ever discovered in Brazil, the Marta Marambaia Valley. The Marambaia River valley Rocha, was found in this region. lies perpendicular to the asphalt road 83 lzm (52 After the 1910 discovery of the Papamel aq- mi.)north of Te6filo Otoni at the hamlet of Ponto uamarine, it became the dream of every garimpeiro de Marambaia. Traveling 20 lzm east of the asphalt to find a great crystal of his own to ensure lifetime road on a good dirt road, you reach the Papamel fame and security. In July 1954, this dream came mine, the source in 1910 of the first great aquama- true for the garimpeiro Wilson Martins da Silva rine find. and the 12 miners he led and helped finance. Dig- During the 70 years following the discovery of ging in the red soil in the side of a hill only 100 m the Papamel, thousands of kilos of aquamarines high, they unearthed the second most valuable were removed from some primary and mostly sec- aquamarine crystal found in this century. This ondary deposits over the entire length of the val- garimpo, the Lavra de Clemente Francisco, was ley. In 1958, two major colluvial deposits were located 6 km northeast of the village of TopAzio, discovered on hillsides overlooking the diggings. only 200 m west of the Pav3o road. At Murundu, 22 kg of crystals were removed. Jules Sauer, the prominent Rio de Janeiro jew- Then, at Mucaia (figure 91, Clementa Fell de Sousa, eler, was in Tedfilo Otoni that morning when he his son Zeca, and fellow garimpeiros found 520 kg got word of the find. He arrived at the mine barely of pale blue aquamarine. In a matter of weeks, over two hours after the discovery, and quickly negoti- 2,000 garimpeiros descended on the hill. Eventu- ated the purchase. This 34.7-kg rounded prism, ally so much fighting erupted over digging sites with superb, uniform color throughout, eventually that the military police had to be called in. In 1968, yielded 57,200 ct of finished gems. A 54-ct stone a few hundred meters from the original find at cut from this crystal appears in the brooch illus- Mucaia, 165 kg of aquamarine were unearthed, trated in figure 1. with the largest crystal (mediumblue) weighing 36 Judging by its rounded and battered condition, kg. And in 1978, an 18-year-old garimpeiro found the aquamarine appeared to be river-rolled, that is, an exceptional 3.9-kg prism in the Filipe valley alluvial in origin. But one cannot establish that below the Mucaia hilltop; this aquamarine even- origin with certainty because a stone can become tually yielded 10,000 ct of superior stones (A. Ta- extremely worn in a colluvial environment when vares, pers. comm.). mixed with abundant and large blocks of quartz, as Another bomba (major find) was unearthed on is often the case with aquamarine, which usually May 20,1964. Five lzm west of the highway and the occurs in pockets adjacent to or near the quartz hamlet of Ponto de Marambaia, a garimpeiro dis- core of the pegmatite. covered four pieces of a crystal that produced some Before it was cut, this stone was appropriately of the highest quality, darkest blue aquamarine named after a beautiful woman, Marta Rocha, ever recorded. The four pieces that comprised this Miss Brazil of 1954. To this day, the subject of etched and abraded, doubly terminated crystal superb cut aquamarines doesn't come up in Brazil were found by Abelo Ferreira in red lateritic soil without mention of Marta Rocha. Some stones more than 6 m under the top of a hill at the Pine from this material can still be found, but they are Tree (Pinheiro) mine (Bastos, 1964; A. Tavares, dearly held and carry a premium (Bastos, 1964; pers. comm.). Less than 2 kg of additional small Abreu, 1965). stones were found by Ferreira in this classic eluvial The discovery of the Marta Rocha aquamarine deposit. triggered another "rush," and thousands of garim- This material was said to have the color of fine peiros overran the hillside and valley below, com- blue tourmaline (Sinlzanlzas, 1974, 1981). When pletely devastating the area. Land damage was so the nearly cylindrical crystal was reconstructed, it extensive that the farmer who owned the land had measured 68.5 x 10.9 cm (27 x 4.3 in.) and weighed to move his cows off the property because there 22 kg; it was almost entirely clean. was nothing left for them to graze on-only bare Agenor Tavares, a well-known Te6filo Otoni 90 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 'diggings nm thefulllengthof the Macmbaiti valley on the low residual hfi wezlooking Moxambdi*~ Cresk At the hei&t of pmducUon, 2,000 misers mxked the hillside <£gKiag at Mwaia. This topography is typical of the mtdw Te6fHo bod-~arambaia pegmatite district gem dealer, was living in nearby Padre Paralso tually hit a pegmatite, but it produced only 5 kg of (formerlyAqua Vennelha) when he heard the ex- aquamarine plus colorless topaz and some citrine. citing news.The first dealer to arrive at the site, he As with the Malta Rocha, die location yielded no purchased the four pieces of the crystal directly additio~ibonanza of aquamabe. Thetwo fa- from Ferreira for one hundred million cruzeiros menus crystals graphically illustrate the hstra- ~oughlyUS$45,000 at that time). Although tfce tions of gemstone muring in Brazil: the only thing price he received was enormous for the garimpetro consistent about such discoveries is their incon- [and very small given the thousands of carats of sistency. Although of different hues, these two faceted stones it would producek Fe^teu'aJsdream crystals are both touchstones by which the highest did not end happily. He quickly started on an ex- quality aquamarines ate measured. tended celebration spree-and died two years later, totally destitute. Trfis Banas Valley. The TI& &mas (Santa Cruz The three darker pieces of this aquamarine River)valley lies south andruns roughlyparallel to were sold to Abdul MiUah and Joiin Pessoa. The the Marambaia valley; it crosses highway BR-116 fo~th~piece,weighing over 7 kg was sold to the at the village of Catugi (fonneriy called Trb Sehb.de Taneira This Wtet colored Banas). piece was the fimt to receive the name IV (Quarto) The first garimpos were started in the 1930s Wtenario to .commemorate Rio de Janeiio's amid great activity at Font Alete, 6.5 kin south of 400th.apmiyersaiyf Thia piece was cut into 15tOD0 the village of T&a Bawas. la 1967 and 1968, some ct dmi&i~-~d~aquamarine [A, Tavam and of the largest aquamarine deposits ever found H. St-, pers. cqnmi-.L The stones cut from the anywhere were mined in this valley and the sw- other three pieces-all of whieh were much darker rounding low-lying residual hills. At the height of than the first-are also refeared to as Quarto Cen- production, many aquamarines were found 1 km teflario and are actually responsible for the repu- west of highway BR-116,just west of Catugt, but tatam, oftbis famous crystal. most of the famous TI& Banas production- was Agenor Tmmes later abtakd he mining found east of the highway. @s to the Pine nee mine; using hvybd- dozers, he spent six full months looking for addi- The Pioneer (Pimeha) AKoe and the Dawn Star tiw aquamarines. Deep in the red earth he even- Aquamarine.. On October 10, 1967i 5 km south- ;. ;. 8 Gem Pegmatites of Minas Gerais rine crystals in histq. This sdmine-a series of eluvial pits unrelated to any primary pegmatite body-produced over 1,500 kg of superior aqua- marine crystals. According to extensive research done by the author, all of these aquamarine crystals, with the exception of the 4,500-ct specimen pictured on the cover and in figure 7, were destroyed by cutting-a tremendous aesthetic and scientific loss. This specimen, which was dug by Colatino Ferreira, survived only because it passed through a series of crystal collectors rather than cutters. Figwe 10. One-fourth of the Dawn Star crystal Figure 11. This hillside at the fos6 de Sousa (originally 1 m long x 18 ova in diameter) and workings of the Tx$s Banas deposit has been someof thestones cut andbeat treatedfrom other totally stripped by the-hwdiedsofpits dugdmiw sections of the same piece. ThIS photo, by Richazd hheight ofminiagitt this region {1968).Note the G&es, was taken in Te6filo Otoal in late 1967. white. kaolin dumps on the higher slopes, crescent-shaped asof tunnels into the cduv1wa, and the inselbergs, and garimpeiro east of Catugi and highway BR-116,a government shanties &kg from the valley floor. Photo by bulldozer was carving a road up to the top of a hill Frederick H,Pough. where a microwave relay station was being built near a Sugar Loaf-like prominence. Near the top of the hill, the blade of the bulldozer rolled a large aquamarine crystal out from its hiding place onto the side of the road, where it lay unobserved by the bulldozer operator. However, seven men who had unsuccessfully sought employment at the micro- wave tower passed the bulldozer on their way back to Catugi, and as they stopped to examine the cut in the side of the hill, they found the 19-2-kgaq- uamarine. Ecstatic over their discovery, they took turns carrying their treasure hack to the village of Catugi. One of the first gem dealers contacted was the same Agenor Tavares of Quarto Centenario fame. Tavates rushed northward and again man- aged to anive before the multitude of dealers who soon followed. He made his deal with the leader of the group, Zeferino dos Smtos, and agreed to buy the stone for the equivalent of US$30,000. The I.O.U. was scribbled on the paper liner from a pack of cigarettes. Eventually, Tavares decided to share the stone (andhis indebtedness] with three other dealers. It was subsequently named the Estrela de Alva, or "Dawn Star." The crystal was almost 100% gem clean (figure 10): Mr. Tavares's 26% portion cut 8,017 ct of fine gems (A. Tavares, pas. corn.; Gaines, 1976). The source of this stunning crystal became the Pioneer mine, which proved to be what was prob- ably the greatest deposit of fine-quality aquama- 92 Gem Pegmatites of Minds Gemis Figurer 12. Working on the valley floor at Ti& Banas, these garimpeiros must con tend with the c~astast flooding of their offuvialpits. Staking of the pits to avoid cave-ins is one solution. Note the layers of multicolored sand and clay, typical of alluvial deposits, in the back wall. Tr6s Banas Deposits. When the Pioneer mine was on for years (figure 11). The two major mining discovered, thousands of garimpeiros descended areas on this small part of the cirque became on the area; as was usually the case, only a few pit known as the Lavra Josede Sousa and Lavra Matto diggers were successful. Seven months later, in Frio. May 1968, massive deposits were discovered less Within 40 days of its discovery, this new find, than a kilometer north over the crest of the called the Tr& Banas deposits, produced over microwave hill and down the adjacent Trh Barras 1,000 kg (one ton) of gem-quality crystals, albeit valley. The partially worked pits below the Pio- paler in hue and rougher in appearance than those neer mine were abandoned in great haste, as the from the nearby Pioneer mine (Pough, 1968 ; ROW, garimpeiros poured into the adjacent valley, 1968). These new hillside deposits extended down Within a few weeks, they had set up their shanty the valley floor to the Santa Cruz stream, and towns on several sites-mostly on the valley floor. aquamarine-bearing alluvium was found several Living conditions for the garimpeiros were ap- kilometers west back to and even crossing high- palling. Thousands of miners huddled in shacks way BR-11 6. Alluvial [placer)pits-cellar-like ex- with only a few huts set up to provide for their cavations that tended to fill with water-were simple needs. Women and children were seldom eventually dug over the entire length of the valley. present at this discovery [Pough, 1968). The gem-bearing gravel layer [cascalbo1 was found Nevertheless, the miners attacked the 200- approximately 3 munder the valley floor, buried in m-high hill with such ferocity that, according to many layers of multicolored clays and sands Pough, in only a few weeks the once tree-clad (figure 121. slopes were totally denuded, transformed into a A few weeks later, three miners investigating prairie-dog village of burrows and red soil dumps; the activities of a group of vultures 3 kmsoutheast the entire steep, raw, red hillside was scarred from of the Pioneer mine found aquamarine exposed on top to bottom, as if the excavation had been going top of the ground where the vultures had landed. Within a few days, they dug over 600 kg of dean uimarhe. Large amounts of aquamarbe my but pale aquamarine. The Sexra do Umbu [Vulture come from this area in the future, but only with Mountain.) deposits produced ova 2@00 kg of the mechanized (strip]mining of the alluvium (just aquamarine in the next few months (Roiff, 1968; now beginning), since the gafimpeiro population R. Nash and Hà G.Kennedy, pers. connn.]* has diminished so dmtically. Duhgihe author's -tion at the aquamarine "crystals" 1983 visit to the Marambaia and Tr@s Barras vd- found in various parts of the Tr6s Barras deposits, leys, only a handful of catras ware in operation. from the top of thehill to the bottom, of the valley several kilometers away, clearly illustrates how JEQUmNHONHAMVER &e physical condition of the gem specimens re- PEGMATITE DISTRICT lates to the distance traveled from the primary North oE thqTe6filo Otoni-Maraoibaia pegmatite pegmatite. The crystals found in the eluvial, wl- district, at Itaobim, highway BR-116 enters the Iuvial, or [occasionally)primary deposits ness the JequitinhonhaRiver pegmatite district. The east- top of the hffl, in conjunction with white kaolin, ern and westem limits of this rich aquamarine were etched but not warn and had good tamha- district can be reached by dirt road MG-367,and dons [amto the crystals pictured in this arti- the northern limits are wily acmssible md well del. Crystals found in colluvial pits farther down defined by the northern villages of Salinas, Pedra the hill (where no kaolin showed on the dumps) Azul, and Pedra Grande (see figure 21. were badly abraded, with pits and cracks iron Thousands of diverse pegmatites and their stained horn thered clay. Two large "crystals" (50 associated secondary deposits occur in this region. kg and 32 kg, respectively} found on the lower A tremendous network of creeks, streams, and slopes had no terminations and were merely bro- rivers drains the interlaced system of valleys and ken cores of what must have been much larger basins of the JequitinhonhaRivet watershed, with cry~tds.The awesfound in thevdey &or aquamarine deposits occurring over the entire [alluvial deposits) were found with ancient river 250-km1155 mi,]length of this pegmatite district. gravel, they were well worn and nearly rounded. The aquamarine-bearing pegmatites of this Although these aquamarines were much less region are geochemidy very &i& to those of common and much. smaller than. those found the Tedfilo Otoni- Marambaia district, except closer to the primary deposit, the material itself that very little topaz of any type has been found was much leaner; interestingly, the color was here, indicating the lack off luorinein the magmas. generally better, too (Pough, 1969; Lucid, 1980). Also, the region overlaps with the Aragual-Itinga green tourmahe disuict dong the Jquitihnha Fume Production &om the TeAFdo Otoni- River; therefore, green and blue-green tourmalines Marambaia Pegmatite District. It is likely that appear in many decomposed pegmatitea but al- massive deposits still remain in this fegion; ody a ways separate from any existing aquamarine de- small percentage of the more obvious and more posits. Likewise, in the west near Coronel Mum easily accessible deposits have been exploited, and and Barra de Salinas, there is some overlap with the relatively few are being mined today IR. Nash, K. hawd-sdhaS t0Wd.h~di6~~t dIE Mawar, pets. comm,).In the 1960s, a gem dealer north. The Plant valley ruiming south from could purchase 3 -6 kg of rough aquamarine per Taquaral is the source of the famous Maxixe week from miners&At this writing, however, only beryls. a few grams are available to each dealer in an aver- The earliest reported discoveries of aquama- age week- In the last two years, the thee largest rine in this region were made by a fanner in 1903 at pieces recovered have been only 0.9-2.9 kg. Ilha Alegre (Happy Island) on the banks of the Unfortunately, accurate production figures, or JequitinhonhaRiver near the vihge of Sao Pedro even close estimates, for the various gemstone de- do Jequitinhonha.Many secondary deposits have posits in Brazil are impossible to obtain since die been found on low hills on both sides of the river. system of monetary regulation encourages the According to Fertandes 119051 and Oakenfull quiet movement of gemstones without official ( 19221, the Happy Island deposits produced many records. large (upto 9 kg], suptzb aqmand gdda The Tedfilo OW-Marambaia pegmatite belt beryls. As recently as 1972, this same deposit pro- historically has been Brazil's major supplier of aq- duced a 65-kg rounded, good-quality blue-green specimen, which was named Cachacinha (a small shot of nun) and subsequently sold in Idar- Oberstein (A. Tavares and R,Nash, pa.comm.}. Three other major aquamarine deposits in this dis- trict wilI k &mm,ed 4ere: Fatalem, Neb,and Comnel Murta (the Frade mine) Fortaleza. The city of Pedra Azul blue stonel, lo- cated 80 km north of ltaobim, was oBgiiMlly called Fortaleza because of the fortress-like inselbergs that surround it. Exceptionally clean chunks of aquamarine, some up to 12 kg, have been produced from a nearby altered pegmatite at Laranjeiras since about 1910. Etched masses were common from this mine, but sharp crystals were never found. One of the largest, totally clean pieces was mined in 1935 and waghed 8 kg. Thebpi* firm of Oacar Machado cut threemajor stones from this piece: the two "smallerv stones were 293 ct and 910 ct, respectivelyi the third, which was pre- Figure 13. One of the small (ooprcsdmatdy S ct) seated by the Brazilian government to U.S. Fxesi- but superb Coronel Mwta uguumaxines. Photo 0 dent Franklin D.Roosevelt in, 1937, was an hued- Hdda? Erica Van P& courtesy offices Saner ibie 1,285 ct [Calmbach, 1938), This last stone, {Saner, 1982). possibly the largest cut aquamarine in existence, can be seen at the Roosevelt Museum in Hyde Park, New York. Two-kilo pieces of rough were Medina now, although 3,000 ct from this deposit common from this mine. were produced in October 1983. The mine itself consisted of a very large open- To the author's knowledge, the largest, most ing on a hillside, with the decomposed primary intense faceted Medina aquamarine is an octago- pegmatite at least 15-18 m wide. The mine has nal 107-ct stone in the collection of Kalil Elawar in beeninactiveformanyyears, but attempts arenow Tedfilo Otoni; the 7.9-kg crystal from which this being made to reopen it. Many exceptionally clean stone was cut in 1978 yielded, a total of 8,000 ct of 0.- and dark aquamarines from dong the entire fine gems (K.Elawar, pas. corn.). . Jequitinhonha River valley have received the meFortala in honor of th& resemblance to Coronel Murta (Frade mine]. The city of Coronel the high-quality gems found at this locale Murta, on the banks of the JequitinhonhaRiver, [Sinkankas,1974, 1981). was founded around 1830 by a retired colonel of thatname. Within6hof thecity byrdisa Medim The village of Medina is located near a prominent inselberg that is visible from a great mountain range 45 km north of Itaobim on high- distance. As one approaches Coronel Murta from way BE-1 16. Many secondary deposits were found Araquai, the back side of the inselberg looks like a in the valleys and basins of this mmm~range# @antre,ching with a fat belly. when colh but most of the best aquamarines from this locale vial and primary deposits were discovered at the were taken from primary deposits still encased in base of the inselberg early in 1973, the aline was the host gneisses of these mountains. Hundreds of given the name Mba do Frade priar mine]* Few tunnels (adits)have been sunk attempting to teach people in the trade have heard of Srade mine aq- the primary pegmatit-, and dm- of workiw uamarine, but nearly everyone has mameled at the were very successful, producing much of the finest small but stmdqblue stones howsimply as quality aqumaine to come born Bdin recent Cormel Murta; they are one and the same (figure years (again, see figure 11. Mining conditions and 1q. terrain are similar to those of the Frade mine dis- In 1973, Boacio Moura Murta, a great-great cussed helow. hatno aquamadm ig found in grandson of the founding colonel, led a group of GEMS & GEMOLOGY Suayayr 1584 95 five garimpeiros to dig in the red soil on Murta% its crystals as the hill ddawayf forming fhe p~qmwhweaqmdebdmfodThe lower duvial deposits, diggings were began in anorth-southvalley 1,200 During 1974, the garimp* began attacking m long that rises gradually for 750 m and then, large outcrops of this pegmatite even higher on the abruptly, becomes very steep for the last 450 m, hill by digging large caves (figure16). Later that peaking on a bill overlooking the city of Colonel same year, they started a labyrinthine series of Murta only a hundred meters to the west of the tunnels in the primary pegmatite 120 m below the giant Frade insdfaeig (figure 14). top of the ridge at the far north end of the valley. The first valley-floor diggings, some as deep as These tunnels extended deep inside the mountain, 3-4 in, exposed only loose crystals in the red soil entering only 30 m from the main fame shack. In of die colluvid deposit (again, see figure 6).But this tunnel .system, the pegmatite vein has been within a few months, an eapandted gairimpeiro cleaned out completely for 60 m inside the moun- work force of more than a-hundred men enthusi- tain, leaving nothing but the sehist wall rock and astically extended their pits and tunnels over some support pillars. literally half thevalley, up the slopes of thebills. In As the miners tunneled deeper into the hill- the higher regions, after digging only a meter or so aide, the directioi~ofthe veins indicated that the into the colluvial soil, they began to strike the pegmatite might continue straight through the hill primary pegmatite wall, which had been intruded with an outcrop on the opposite side. Although into the east side of the valley for what appeared to exploration in this new area revealed no outcrop be at least 750 m in and-southdirection (we where the garimpeiros had hoped to find it, in the 151, This was the pegmatite that had sloughed off course d their prehmaqdigging they discovered extensive crystal deposits in the eluvium- directly on top of the lull. Eventually, colluvial deposits Figure 14. The mine shack and maia tunnel at were discovered exteacfaog at t 150 m down the Piade mim are only a short distance from the lea$ laselbexg after which the area is named. hillside lacing CordMurta Tillage. Again, in some locations, after digging down only a meter or - -7so, they encountered the primary pegmatite. It seems, then, that the pegmatite they had been working on 120 m. below had been intruded clear through the top of the hillj and as the hill eroded away, it had shed its crystals down the slope. A monumental excavation project began, and eventually the entire top of the hill was pitted, dug up, and turned over repeatedly, until the area re- sembled an artillery range. In the process, though, thousands of crystals were found. Oecuxence. This pegmatite is unusual for its long, narrow shape. Mineralogically, however, it is typi- cal of other deposits in this district, Specifically, black tourmaline is abundant, as are a+ plates of biotite mica, big smoky quartz crystals, and approximately 25-cm unaltered feldspar crystals (reflecting the unaltered state of the primary pegmatite body}. In fact, hundreds of tons of fine feldspar lie on the dumps, ualdle,because of the 450-km &stance to the marketplace in Governador Valadaies. The Rade mine, like most in the Arasuaf-Salinas-Ititiga region, has to meet expenses strictly through the sale of gem rough. There were two unusual occurrences at this time, however. First is the presence of green mi- GEMS & GEMOWGT Stmima 1984 Figure 15. After only a meter of tunneling, this garimpeiro has reached the primary pegmatite (note the white feldspar) at Frade. crocline (amazonite), which was common and- along with black tourmaline-was the best indica- tor that gem aquamarine was close by. Second, a few gem crystals of rose tourmaline, some as long as 4 cm, were found in the main tunnel. The lithium ,and manganese required to reduce rose tourmaline are seldom found assoct ated with aq- uamarine. No topaz or lzunzite was found. Figure 16. This garimpeiro is indicating the width of the pegmatite body in one of the large caves Current and Future Production. When the Frade excavated on the upper slopes of Frademountain. mine reached its peak production in 1981, the 200 kg of aquamarine recovered meant an average of only one kilo per garimpeiro. All of the crystals cause there are additional "virgin" areas of the were highly fractured; 70-80% of the pieces pegmatite and colluvial deposits still to be ex- weighed less than 100 g (3ozs.). The highest qual- ploited; however, the extent of the reserves is ity aquamarine was found in pockets in the speculative. Because of the expense of hard-rock pegmatite. The largest piece of rough weighed a mining, the shortage of manpower, and the un- little over 260 gj the largest intact (but internally proved reserves, it is the author's belief that this fractured) crystal was only 7.6 x 3.8 cm (3 x 1% unusual occurrence will continue to produce only in.). These production figures contrast sharply very small quantities of fine aquamarine in the with those from Trks Barras, although the best years to come. Although hundreds of alluvial pits Coronel Murta color is far better than the best Tres have been dug near Coronel Murta, as might be Barras color. expected they have produced only a fraction of the In fact, the best aquamarine from this mine is material found in the primary deposit. among the finest in Brazil. Yet, because the crys- tals are so fractured, intense faceted stones are OTHER AQUAMARINE DEPOSITS usually less than 1 ct, although totally clean stones The Ara~ualRiver-Capelinha-Malacacheta Dis- as large as 4-5 ct do exist and 3-ct stones are not trict. Along the Ara~uafRiver on the north and its uncommon. Ten-carat stones have been faceted tributaries on the south, in the area enclosed by the hut they are not completely clean. cities Minas Novas, Turmalina, Capelinha, Production has dropped off sharply in the last Malacacheta, Novo Cruzeiro, and Lufa, hundreds three years, and only 70 garimpeiros work the of valleys and basins have yielded notable primary Frade mine today. The mine owners insist that and secondary aquamarine-bearing deposits there will be considerable future production be- (Calmbach, 1938; Sinlzanlzas, 1974, 198 1; Pecora Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 Figure 17. This 6-ern heliodor (golden beryl) from near Colatina, E.S,, accompanied by a 40.4-ct faceted mate, is representative of some of the fine material that has been found in the area around northeastern Minos Gerais. Photo 0 Harold es) Erica Van Pelt. et al., 1950). Additionally, deposits of both gem secondary deposits [Calmbach, 1938; Sinlzanlzas, beryl and tourmaline have been found in the 1974, 1981). northernmost portion of the three rivers GravatA, Three of the largest single aquamarine crystals Setubal, and Sucurid and of the larger river Araguaf ever recovered were found in the Governador Val- (to the city of Aragual), as early as the 1890s adares region: a 108-kg piece at Ariranho on the (Sinlzanlzas, 1974). The countryside surrounding Rio Bugre, in 1942 (Ball, 1943);a 25.4-kgpiece near virtually all of the cities in the areas shaded in blue Resplendor, in 1946 (Sinlzanlzas, 19741, and a par- on the map in figure 2 has produced significant ticularly fine 61-kg specimen (called the Lucia) quantities of gem-quality aquamarine. found in gravels at Garajad, in 1955 (Abreu, 1965; Sinlzanlzas, 1974). Governador Valadares District. One of the most The quality of the aquamarine varies through- productive regions of Minas Gerais in both volume out Minas Gerais, but most of the gem rough found of gem beryl and size of crystals is the area within a is pale to medium blue-green (heat treated to pro- 150-lzm (90 mi.) radius of Governador Valadares duce a comparable intensity of purer blue). One and embracing the watershed of the Doce and advantage of this gem is that large (15+ ct), totally Suaguf Grande rivers. The countryside surround- clean stones are readily available. ing all of the cities in this area on the map in figure Currently, this region is producing only small 2 has produced major finds in both primary and amounts of aquamarine. There continues to be 98 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 great potential, however; the strip mining of allu- cates the geothermal processes that produce the vial deposits in the Te6filo Otoni-Marambaia rose-colored stones occasionally found in nature. region, in particular, holds promise for significant The largest deposit of morganite crystals ever future production. Judging from the past, major found occurred at the Corrego do Urucum mine in deposits could be found in the vicinity of any of the Galil6ia in 1973. Approximately 300 crystals, cities in figure 2. some weighing as much as 10 kg (22 lbs.), were discovered lining the walls of an immense cylin- HELIODOR (GOLDEN OR YELLOW BERYL) drical pocket. This deposit will be discussed in Top-quality golden or yellow beryl (figure 17) is greater detail in the upcoming article dealing with much rarer than aquamarine, although the best kunzite, which was also found in great quantity at heliodor is not as valuable as the best aquamarine. this locality. Some yellow and golden beryls, when heat treated Other significant deposits of morganite in for 1-12 hours to between 280° and 600° Brazil were all found in Minas Gerais. These in- (depending on the source of the material and the clude Sapucaia (municipality of Galileia), Calisto, inclusions), will turn a pleasing, more salable aq- Minas Novas, and along the Jequitinhonha River uamarine color (no greater in intensity than the valley. No production is currently coming from original yellow or gold); others, however, will just any of these localities. Occasional kilograms of become a lighter yellow. Still others may also turn material, however, have been found recently at the such a pale blue that they are worth much more Salinas mine and at an unnamed deposit near Con- left as heliodor. One can be sure that the best selheiro Pena, which produced some 5,000 ct in golden or yellow stones offered for sale have not 1982 from a single pocket. This rose-pink gem- been heat treated-but that others from the same stone is in chronic short supply; no major deposit crystal were undoubtedly tested. has been discovered since 1973. HeLidor usually occurs mixed with bluish and To the author's knowledge, the two best greenish'iberyls as a small portion of the total de- faceted Brazilian morganites are both at the posit. he author knows of only one mine where Smithsonian Institution: 236 ct and 250 ct heliodor. constituted a large percentage of total (Desautels, 1965, photo on p. 38; Desautels, 1979, beryls produced: Mina Urubu, near the city of photo on p. 39). Santa Cruz immediately east of Novo Cruzeiro. Yellow and golden beryls have also been found in SUMMARY AND CONCLUSION significant amounts at the Marambaia, Medina, Aquamarine is found over most of the northeast- Ilha Alegra, and Farrancho deposits, with notable ern part of Minas Gerais; millions of carats have production also from Born Jesus do Lufa, Dois de been mined since the discovery of the Papamel Abril, Guanhaes, Joaima, Minas Novas, crystal in 1910. Both heliodor and morganite are Sabin6polisI Serro, and Sapucaia as well. Quality significantly less common. Aquamarine is usually gems, however, are always in short supply, espe- heat treated to obtain its optimum blue; heliodor cially large stones. may be heat treated to turn from yellow to aqua- The world's largest cut heliodor, at 2,054 ct, is marine blue; peach- and salmon-colored morga- in the Gem Hall at the Smithsonian Institution, nites are often heat treated to obtain the preferred Washington, D.C. (illustrated in Sinkankas, 1981). rose-pink color. Most of the aquamarine is found in secondary MORGANITE (PINK BERYL) deposits, although much of the darkest material Morganite, the popular rose-pink variety of beryl, has come from the primary pegmatites at For- is also rarer than aquamarine. Morganite occurs taleza, Medina, and Frade (Coronel Murta). Cur- commonly in two "less desirable" color phases: rently, little aquamarine (orheliodor or morganite) peach and salmon. Generally, the rose-pink tints is being produced because of the shortage of garim- are more fashionable. Cut morganites are com- peiro labor and the expenses involved in mining, monly heated individually in a test tube over an although small amounts are coming from other alcohol flame (200°-400°for a few minutes to states in Brazil. Nevertheless, there continues to obtain a delicate pink hue (which is totally stable). be great potential for the discovery of major de- As with aquamarine, virtually all morganite is posits anywhere in the Minas Gerais pegmatite heated by this process, which essentially dupli- area. Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 99 REFERENCES de Diccionari. Imprensa Nacional, Rio de Janeiro. Abreu S.F. de (19371 A riqueza mineral do Brasil. S.L. Bibliog- Freyberg, B.V. (1934) Die Bodenschatage des States Minas rafia Pedag6gica Brasileira, Vol. 102. Gerais, Brasilien. Schweizerbart, Stuttgart. Abreu S.F. de (19651Recursos Minerais do Brasil. Minerals ndo Gaines R.V. (19761Beryl-a review. Mineralogical Record, Vol. metdlicos. Institute Brasileiro de GeogrAfica e Estatlstica, 7, No. 5, pp. 21 1-223. Conselho Nacional de Geografia, Publication #20, Rio de Gesner C. (15651De Rerum Fossilium, lapidum et gemmarum. Janeiro. Gesner, Tiguri. Anderson M. 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(1980) Review of history and survey of present and pp. 21 -34. future mining in Brazil. Report at the 7th Annual Rochester Bassett A.M. (1967) Understanding Brazilian geology helps. Mineralogical Symposium, Rochester, New York (unpub- Lapidary Journal, Vol. 21, No. 2, pp. 306-3 11. lished). Bastos P.M. (1964)A 15.4-pound Brazilian aquamarine. Gems Mawe J. (1812) Travels in the Interior of Brazil. Longman, a) Gemology, Vol. 11, No. 8, pp. 239-241. Hurst, Rees, Onme, and Brown, London. Bastos P.M. (1972)Brazil: land of tourmalines. Lapidary lour- Moore IJ.B. (19731 Pegmatite phosphates: a descriptive miner- nal, Vol. 26, No. 8, pp. 1224- 1229. alogy and crystal chemistry. Mineralogical Record, Vol. 4, Bastos P.M. (1981)Emeralds from Itabira, Minas Gerais, Brazil. No. 3, pp. 103-130. Lapidary Journal, Vol. 35, No. 9, pp. 1842-1848. Moura O.J.M.de (1981)Gems from Brazil. InMetamig, Metais Burns E.B. (19651A Documentary History of Brazil. Alfred A. de Minas Gerais, S.A., Be10 Horizonte. Knopf, New York. Oakenfull J.C.(19131 Brazil in 1912. Robert Atkinson, London. Calmbach W.F. (1938) Handbuch Brasilianischer Edelsteine Oakenfull J.C. (19221 Brazil: A Centenary of Independence, und ihrer Vorkommen. N. Medawar, Rio de Janeiro. 1822 -1 922. C.A. Wagner, Freiberg. Cal6geras J.P. (1904)As minas do Brasil e sua legislaqio. Im- O'Leary O.J. (1970) Locality-Minas Gerais, Brazil. Min- prenso Nacional, Rio de Janeiro. eralogical Record, Vol. 1, p. 73. Cameron E.M., Jahns R.H., McNair A.M., Page L.R. (19491 Paiva G. de (1946) Provincias pegmatfticos do Brasil. Internal Structure of Granitic Pegmatites. Economic Geol- Departamente Nacional da ProduqSo Mineral Divisdo Fo- ogy, Monograph 2, p. 1 15. mento da Producdo Mineral, Vol. 78, pp. 13-21. Caplan A,, Wilson W. (1980) Interview: Allan Caplan. Min- Pecora W.T., Klepper M.R., Larrabee D.M., de Barbosa A.L., eralogical Record, Vol. 11, No. 6, pp. 35 1-366. Frayha R. (19501 Mica deposits in Minas Gerais, Brazil: Cassedanne I.P.. Lowell I. (19821Famous mineral localities: the geologic investigation in the American Republics, 1949. Virgem cia ~apapeg&atites.'~ineralogical Record, Vol. 13, U.S. Geological Survey Bulletin, 964-C, pp. 205-305. NO. 1, pp. 19-28. - Pough F.H. (1968) The Tres Barras aquamarine mine. Lapidary Dana E.S.. revised bv Hurlbut C.S. Ir. 119591 Manual of Miner- Journal, Vol. 22, No. 8, pp. 1038-1042. alogy, '17th ed. wiley & Sons, New ~ork. Pough F.H. (19691Brazil and its minerals. Mineral Digest, Vol. Desautels P.E. (1965) Gems in the Smithsonian Institution. 1, No. 1, pp. 25-32. Smithsonian Institution Press, Washington, D.C. Rolff A. (1968) The aquamarine-bearing regions of Brazil. Lapi- Desautels P.E. (1970) The Mineral Kingdom. Madison Square dary Journal, Vol. 22, No. 8, pp. 1044-1049. Press, New York. Sauer J.R. (1982)Brazil, Paradise of Gemstones. Rio de Janeiro. Desautels P.E. (19791 The Gem Collection: Treasures in the Shigley J., Kampf A. (19841Gem-bearing pegmatites: a review. Smithsonian. Smithsonian Institution Press, Washington, Gems a) Gemology, Vol. 20, No. 2, pp. 64-77. D.C. Sinkankas J. (19641Mineralogy for Amateurs. D. Van Nostrand Dirac F., Ebert H. (19671 Isotopic age from the pegmatite prov- Co., Toronto. inces of Eastern Brazil. Nature, Vol. 215, pp. 948-949. Sinkankas J. (19741Beryl in Brazil, Parts 1-111. Lapidary Jo~~rnal, Dreher 0. (19121 Grosser Aquamarine krystall aus Brasilien. Vol. 28, Nos. 2-4, pp. 324-332; 506-515; 646-655. Centralblatt filr Mineralogie, Vol. 11, p. 338. Sinkankas J. (19811 Emerald and Other Beryls. Chilton Book Eschwege W.L. (1833)Pluto Brasiliensis. G. Reimer, Berlin. Co., Radnor, PA, Fernandes X.P. (19051 Aquamarines and tourmalines at Aras- Souza A.J.A. de (1943) Aspectos da economia da pedras pre- suahy in Minas Gerais. Brazilian Engineering and Mining ciosas.Minera@o e Metalurgia, Vol. 7, No. 36, pp. 257-262. Review, Vol. 2, No. 3, p. 42. Zeitner J.C. (1979)Gems of Brazil. Lapidary Journal, Vol. 33, Ferraz L.C. (19291Compendia dos Mineraes do Brasil en Forma No. 1, pp. 142-155. 100 Gem Pegmatites of Minas Gerais GEMS & GEMOLOGY Summer 1984 NOTES AND NEW TECHNIQUES THE FIRST-ORDER RED COMPENSATOR: AN EFFECTIVE GEMOLOGICAL TOOL By John Ilmarii Koivula This note deals with some gemologjcal applications allel to the perfect cleavage; or quartz, cut parallel for n tool well known to microscopists: the first- to the c-axis. The plates produce an optical retar- order red compensator. In gemological microscopy, dation of 530 to 550 nm. the compensator can be useful in locating interfer- Because of the brittle nature and small size of ence colors and optic figures in birefringent materials the ultra-thin gypsum and quartz plates needed to and in delipeating strain in gemstones. -In polarized- make a first-order red compensator, these com- light photomicrography, a properly positioned com- pensator &in reduce the exposure time required and pensators were poorly suited for use with a low- thus the risk of film reciprocity failure and of poor- power gemological stereo microscope. It was not quality images resulting from random vibrations of until the late 1970s, when the Polaroid Corpora- the microscope and its accessories. tion introduced large-format first-order red com- pensators in plastic sheet form, that the applica- tion of such a compensator became practical for use with a polarizing gemological microscope. The Mineralogists, petrologists, chemical microsco- compensator manufactured by Polaroid is a pro- pists, and crystallographers areal1 familiar with the prietary product, a plastic laminate of undisclosed usefulness of a first-order red compensator in nature, that produces an optical retardation of locating fast and slow vibration directions of light approximately 530 nm. in crystals, in helping determine the optic char- acter of unknown crystalline compounds, and in HOW THE COMPENSATOR WORKS defining areas of strain. Use of this microscopist's Several good texts are available that describe the tool in gemology, however, is virtually unknown. use of the first-order red compensator in the areas While exploring potential gemological appli- of microscopy, optical mineralogy, and optical cations for the classic uses of the first- order red compensator - specifically, enhancing interfer- ence colors and determining areas of strain - this ABOUT THE AUTHOR article highlights a new use for the compensator, Mr. Koivula is senior gemologist in the Applied Gemology Department of the Gemological Institute of America, Santa in the field of polarized-light inclusion pho- Monica, California. tomicrography. Acknowledgments: The author would like to thank Dr. John DeHaas, of DeHaas Optical Engineering and the University of WHAT IS A FIRST-ORDER RED Southern California, and Alan DeHaas, of DeHaas Optical COMPENSATOR? Engineering, for the gift of the first-order red compensator sheet and for their review and comments on this article. Kristi Traditionally, first-order red plates have been con- Koivula also deserves special thanks for her patience in typing structed of a small, thin (approximately 0.0625 the manuscript. mm), uniform layer of selenite (gypsum),cut par- 1 1984 Gemological Institute of America Notes and New Techniques GEMS & GEMOLOGY Summer 1984 101 POLARIZER 1 POLARIZER 1 I 1 f = Fast component direction f = Fast component direction s = Slow component direction s = Slow component direction S = Area of subtraction of retardations resulting in A = Area of addition of retardations resulting in lower order interference color higher order polarization interference color 'ig~ire1. Drawing showing the test subject and Figure 2. Drawing showing the test subject and compensator plate oriented in subtraction posi- compensator plate oriented in addition position tion in a polarized light field when the polar- in a polarized light field when the polarizer izer and analyzer are in total extinction. Draw- and analyzer are in total extinction. Drawing ing by Christine Wilson, after McCrone et al., 1979. by Christine Wilson, after McCrone et a/.,1979, crystallography (e.g., Phillips, 1971; McCrone et et al., 1979) illustrates the "Newton's Series" al., 1979). When inserted in a field of polarized sequence of interference colors. If we can enhance, light, the compensator basically serves to brighten or brighten, low-intensity interference colors either and enhance an image by the addition or subtrac- by subtraction from the higher orders or by addi- tion of optically retarded wavelengths as they pass tion of the lower order, then they will be much through the compensator into an optically aniso- easier to locate and observe. The first-order red tropic subject. When two anisotropic materials, compensator is well suited to this task. one being the compensator, are superimposed in a field of polarized light, addition or subtraction GEMOLOGICAL APPLICATIONS of their individual retardations will occur, depend- The first thing the gemologist notices when using ing on their orientations to each other and to the a first-order red plate is the vivid magenta color polarizer and analyzer. If both the compensator it produces when it is inserted in the light path and the subject are oriented in the position of total between the polarizer and the analyzer when they brightness in the polarized light field (which is 45' are in a position of total extinction. The view away from the vibration directions of the analyzer through the GEM polariscope shown in figure 3 and polarizer) and their slow vibration directions illustrates this effect. (corresponding to the higher refractive index] are It should be noted that the first-order red com- perpendicular or at right angles to each other (see pensator plate is not a filter that is red in color as figure l),then subtraction of retardations occurs, the name might imply. Rather, it is a very pale resulting in lower-order interference colors. If, yellowish, almost colorless, material that gives a however, the slow vibration directions of the com- first-order red or magenta color to a field of polar- pensator and the test subject are oriented parallel ized light. The first-order red compensator has a to each other (as in figure 21, then addition of number of practical applications in gemology, as retardations occurs, resulting in higher-order described below. interference colors; low-intensity blacks, grays, and whites and very pale yellows, oranges, and reds Observing Interference Colors and Locating the are enhanced into the more vibrant first- and sec- Optic Axis. During orientation of a doubly refrac- ond-order colors. The Michel Levy chart (McCrone tive gemstone in the polariscope or microscope, 102 Notes and New Techniques GEMS & GEMOLOGY Summer 1984 crystalline intergrowth, or as halos surrounding solid included crystals - strain will often reveal itself under polarized light conditions as color anomalies in shades of brown, gray, and black. Because of this lack of color intensity, it is some- times very difficult to detect. The first-order red compensator can be used to enhance strain colors and patterns (figures 4 and 5), producing more vivid blues and yellows or sometimes reds and greens. Inasn~uchas strain is commonly present in dia- monds, microscopic examination under polarized light with a first-order red compensator is a help- ful method of separating diamonds from substi- tutes such as cubic zirconia and yttrium alumi- num garnet. Use with Polarized Light Inclusion Photomicrog- raphy. When using polarized light to photograph inclusions, the gemological microscopist is com- monly confronted with low light intensity and a Figure 3. View through a polariscope with the correspondingly long exposure time that all but first-order red compensator inserted halfway makes quality photomicrography impossible. With through the polarized light field. the first-order red-compensator, however, the image is enhanced by a vivid array of bright interference ,, r / as the gepologist searches for an &tic axis, the colors and the exposure time required -and, con- first-orderred plate can prove helpful. Here it serves sequently, the effect of vibrations - is greatly as a means of brightening interference colors that reduced. start to appear as the optic axis direction is If we look again at the polariscope image in approached. Brighter colors are much easier to figure 3, we see how much brighter the magenta locate. It follows that if the optic axis interference side of the polarized light field in this image is. colors are easier to locate, then the optic axis itself When the compensator is used with a gen~ological can be found more quickly. microscope equipped with a light-polarizing sys- tem, the difference in brightness is equally obvious Determining Strain. When present - either as a and also readily measurable with a light metering result of unseen internal disruption, twinning, or system. Light metering showed that the exposure Figure 4. Left-Included crystal of diamond in diamond, photographed in polarized light without the compe;~sator.Exposure time, 1 minute 25 seconds. Right-the same. crystal photographed in polarized light with the ^*"-order red compensator. Exposure time, 22 second' Hagnified 50 x , Notes and New Techniques GEMS & GEMOLOGY Summer 1984 103 I I Figure 5. Left-Monazite crystal in an African rhodolite garnet in polarized ligi~twithout the first- order red compensator. Exposure time, 3 minutes, 13 seconds. Right-Monazite crystal but with the first-order red compensator inserted. Exposure time, 25 seconds. Magnified 50 x . time required to properly expose film with an ASA first-order red compensator into the field, the of 160 when the polarizer and analyzer are in 90 inclusion picture (figure 4, right) is immediately extinction is over 10 hours. With insertion and decorated by an array of vivid strain colors and proper orientation of the first-order red compen- the exposure time reduced to 22 seconds. sator in the field between the polarizer and ana- The second subject, a rhodolite garnet, plays lyzer, the exposure time is cut to less than one host to a euhedral monoclinic crystal of transpar- minute. The brighter the image is the less the ent yellow monazite. As shown in figure 5 (left), required exposure time will be. taken under polarized light without compensator, Although the above-mentioned difference in strain in low-intensity colors is visible around the exposure time is dramatic, no inclusion subject radioactive monazite. The exposure time was three was present in the light path to demonstrate the minutes and 13 seconds. In figure 5 (right),taken true value of the compensator plate to the gem- with the compensator in place, the image is now ologist-photomicrographer. To illustrate the point, alive with bright interference colors; time for the three test subjects showing a wide range of optical exposure was only 25 seconds. properties - a diamond, a garnet, and a rock crys- The last test subject, a colorless quartz, con- tal quartz, all with inclusions - were selected. tains a number of small, noninterfaced, uno- The first subject, the diamond, has an inclu- riented, slightly distorted quartz crystals. Without sion of another diamond that shows only partial polarized light (figure6, top), only a few faint areas interfacing, making some of the edges virtually of the quartz inclusions are visible because they invisible as they blend with their host of the same have virtually no interfacial separation and the refractive index. The diamond within a diamond same refractive index as their host. This trans- was photographed first using only the polarizer mitted light image was recorded in one second. In and analyzer in extinction. The photograph, shown figure 6 (bottom left), under polarized light, all of in figure 4 (left),reveals a great deal of lattice strain the quartz crystal inclusions are now visible. in and around the inclusion. The exposure time However, the exposure time was 18 seconds. With was one minute and 25 seconds. The strain colors the first-order red compensator (figure 6, bottom in this photomicrograph are all of low intensity right), the included crystals are still vivid but the and the image is quite dark. With insertion of the exposure time was reduced to 8 seconds. Notes and New Techniques GEMS & GEMOLOGY Summer 1984 Figure 6. Top-These inclusions of rock crystal quartz in rock crystal quartz are virtually invisible in transmitted light. Exposure time, 1 second. Bottom left-The same inclusions of quartz in quartz shown above become visible under polarized light. Exposure time, 18 sec- onds. Bottom right-Use of the first-order red compensator reduced the exposure time in polarized light for the image shown at left to 8 seconds. Magnified 20 x . CONCLUSION aids efforts to locate an optic axis direction in a Comparing the photographic images with their doubly refractive gemstone by making the loca- corresponding exposure times shows that the first- tion of interference colors, as an optic axis is order red compensator has something to offer the approached, much easier. gemologist who is interested in polarized light photomicrography. The technique is easily adapted to any standard stereo gemological microscope and the results can be worth the effort. Additionally, the first-order red plate enhances REFERENCES strain colors, making strain areas more easily vis- McCrone W.C., McCrone L.B., Delly J.G. (1979)Polarized Light Microscopy. Ann Arbor Science Publishers, Ann Arbor, Ml. ible and thereby simplifying the location of strain Phillips W.R. (19711 Mineral Optics-Principles and Tech- centers. In many instances, the compensator also niques. W. H. Freeman and Co., San Francisco, CA. Notes and New Techniques GEMS & GEMOLOGY Summer 1984 105 EDITOR C. W, Fryer GIA, Santa Monica CONTRIBUTING EDITORS Robert Crowningshield LAB NOTES Gem Trade Laboratory, New York Karin N. Hurwit Gem Trade Laboratory, Los Angeles Robert E. Kane Gem Trade Laboratory, Los Angeles AMETHYST, Unusual Natural Inclusion Before synthetic amethyst was avail- able on the market, we seldom felt it necessary to examine every ame- thyst under magnification to observe any inclusions that might be present. However, the advent of the synthetic material has made it necessary to study the inclusions in each stone to determine, if possible, natural or synthetic origin. Figure 1 shows an amethyst that came into the New York lab for identification. The in- clusions, which resemble a pie- shaped galaxy of red stars, are goethite, an iron-oxide mineral. While the presence of goethite es- tablishes the natural origin of the stone, this is the first time we have observed this unusual zonal distri- bution in amethyst. R. C. CUMMINGTONITE-GRUNERITE, A Series in the Amphibole Group Recently submitted to the Los An- Figure 2. This amphibole rock -measuring 36.3 x 23.0 x 21.2 mm -is geles laboratory for identification slated for use as an ornamental stone. was a piece of rough material with one mineral within that portion of Figure 1. Unusual zonal distri- one polished face that consisted of an the rock. bution of goethite inclusions in opaque black center section bordered A minute amount of powder was amethyst. Magnified 30 X. by two opaque yellowish brown scraped from the blaclz portion for areas (figure 21. X-ray diffraction analysis. The re- When the specimen was exam- sults of the X-ray powder diffraction ined with the unaided eye, white in- showed that the blaclz material is a clusions were observed scattered throughout the opaque blaclz mate- rial. Testing of the blaclz area with a Editor's note: The initials at the end of each refractoineter revealed vague read- item identify the contributing editor who ings of 1.54 to 1.55 and 1.64 to 1.65, provided that item. indicating the presence of more than 0 1984 Gemological Institute of America 106 Gem Trade Lab Notes GEMS & GEMOLOGY Summer 1984 rock consisting of at least three dif- with coated stones became cautious stone. This stone was highly bire- ferent minerals, one of which is an when the stones looked "wrong" in fringent, .029, with a refractive index amphibole, probably in the cum- the color grader. However, using the of 1.671-1.700. The optic character mingtonite-grunerite series. There same "double lighting" recom- was biaxial positive; a biaxial optic were not enough diffraction lines to mended originally by Mrs. Miles, figure could even be obtained on the identify the other components. very discrete coatings were detected. pavilion of the stone near the culet. Nongemological, probably petro- For the most Dart the actual colors of No absorption lines were visible in graphic, tests would be required to the stones before coating have been the hand spectroscope. The fluores- identify the rock type. found to be H or I. With the coating, cence was faint chalky greenish This material is reportedly from some might have been graded as high white to short-wave ultraviolet radi- a deposit in North Carolina. The cli- as G if they hadn't had that suspici- ation, but inert to long-wave ultra- ent who submitted the sample for ous grayish appearance. In at least violet radiation. We determined the identification explained that the one recent case, the client submit- specific gravity by the hydrostatic owner of the specimen had several ting an uncoated stone that had been method to be 3.31. The properties of hundred kilos of this material and found to -grade H asked for a color this stone indicated diopside, despite planned to market it for use as an recheck within a week after the re- its unusual color. X-ray diffraction ornamental gem, that is, for carvings, port had been issued. When the stone confirmed our other test results. cabochons, and inlaid stones in jew- was reexamined, it was found to have elry. The jeweler-gemologist should a coating that gave it an F to G ap- not be surprised, therefore, if he en- pearance, but with a grayish cast. counters this material at some future Clearly, the laboratory was being time. R. I<. used. For the most part, the coatings seen recently are beautifully applied and could be easilv overlooked. DIAMOND' Sometimes only a ghostly band on Coated ~ia~~~d~one side of the girdle can be detected. In other cases, the band lies on both Longtime readers of Gems ed the oavilion and the crown side of the Gemology will no doubt recall the girdle, as in figure 3. The coating is so important article by Eunice R. Miles thin that no effort has been made to on "Diamond Coating Techniques analyze it. However, its resistant na- and Methods of Detection," which ture suggests that it may be similar appeared in the Winter 1962-63 is- to the blue-to-violet hard enamel sue. At that time, the practice of (flux)reported by Mrs. Miles in 1962. coating diamonds had become so in- R. C. sidious and damaging to the trade Figure 3. The arrow points to that in September 1962 the New Dendrite-like Inclusion areas of coating that are evident York state legislature enacted a law The Gem Trade Lab Notes section of on both sides of the girdle of this prohibiting the use of the technique coated diamond. Magnified 30 x. unless it was fully disclosed to the the Spring 1984 issue featured a purchaser. photo of a stepped laser drill hole Since then, the Gem Trade Lab- connecting several inclusions. Fig- Figure 4. This unusual dendritic inclusion in diamond resembles oratory has seen only about three or ure 4 shows a rare, step-like natural a step-like laser drill hole. four coated stones a year. In fact, dendrite-like inclusion that appears Magnified 20 x. some of the more recent staff nlenl- to connect several included crystals bers had never even seen or tried to in a diamond that was submitted to color grade such a stone. Approxi- our New York laboratory for grading. mately six months ago, however, an R. C. unusual number of coated diamonds started to come in to both the Los Angeles and the New York labs. DIOPSIDE These stones were not being subn~ittedby appraisers or jewelers A few months ago, a gemologist from who were suspicious of the color, but Sri Lanka asked the Santa Monica lab rather by cutters and brokers. to help in the identification of a Twenty years ago, graders familiar 0.72-ct emerald-cut grayish lavender Gem Trade Lab Notes GEMS & GEMOLOGY Summer 1984 107 dyed gem materials was then im- plemented. When an inconspicuous brown area was rubbed with an acetone-soaked cotton swab, how- ever, absolutely no stain appeared on the swab. Inasmuch as some dyes and stains are not removed from cer- tain gem materials with acetone alone, we decided to try a 10% hydrochloric acid solution next. When the same area of the carving was rubbed vigorously with a cotton swab soaked in the acid solution, a light brown stain was produced on the swab. This evidence, together with the unnatural appearance of the piece, led us to conclude that this Figure 5. Artistically stained nephrite carving, 23.4 x 7.2 x 9.5 cm, carving had been artistically stained in a manner similar to that com- monly seen on nephrite jade carv- JADE appearance. In addition to somewhat ings. Since no attempt had been Artistically Stained Nephrite large areas of brown color on the made to enhance the color of the en- The Los Angeles laboratory received carving, nearly all of the shallow tire carving, with the dye or stain for identification a translucent to carved depressions (see the wing having been applied only in selected opaque variegated pale green and areas of figure 5) showed brown col- areas to highlight the details of the brown carving of two birds which oration in contrast to the pale green carving, the following conclusion measured approximately 23.4 x 7.2 x raised areas directly next to them. was stated on our gem report: 9.5 cm. Subsequent testing of the This appearance very strongly sug- NEPHRITE JADE, with some areas carving revealed that it was nephrite gested that the brown color in these of artistic staining. R.K. jade. areas was probably caused by artifi- During preliminary examina- cial staining or dyeing in an attempt Dyed Nephrite tion, we observed that the variegated to highlight the carved details. Unlike the artistic staining described brown coloration was unnatural in The least destructive test for above, somenephrite is being dyed so that the color is changed throughout the material. The first potentially Figure 6. A strand of dyed green nephrite beads, each approximately commercial quantity of green dyed 9 mm in diameter, nephrite we have encountered for some time were the cabochons re- ported in the Spring 1984 issue of Gems et> Gemology. Figure 6 shows the first strand of beads of this mate- rial submitted to our New York labo- ratory. The absorption spectrum of these 9-mm beads is very similar to that seen in the more familiar dyed jadeite, indicating that the same dye may have been used. If so, the stones would probably be just as susceptible to fading as dyed green jadeite is. R. C. PEARLS Imitation Mabe Pearls The two items shown in figure 7 were brought to our Los Angeles lab- 108 Gem Trade Lab Notes GEMS & GEMOLOGY Summer 1984 uniform material, These "Mabe pe<~rIs"were certainly thc most real- istic imitations we have encoun- tered. K.11. tJi~~~sualCultured Pearls &I attractive air of somewhat flat- tened 18-1nmpearls on pendant ear- ring:; [ijgur(-:8) fluoresced strongly to X-radiationt indicating irest~water origin. Although the X-radiograph taken in the flat direction (figure 9) was inconclusivet that taken with the pearls on edge (figure 10) shows flattened lentil-shaped nuclei. These Figure 7. Imitation Mabe pearls. The finished "pearl" on the right are the first freshwater culturecl measwes 17 x 15 nim. pearls of this type we have seen in the New York laboratory. oratory for identification. They were producing the appearance of a de- Coincidentallyt the New York being offered on the market as "Mabe marcation line within the otherwise laboratory also received a pair of pearls." Gemologists sho~ildre- button-shaped pearls set in stud ear- member that a Mabe pearl is an in- rings for testing (figure 11). They duced blister pearl that has been cut displayed weak to moderate fluores- from the shell and the nacreous *cence when exposecl to X-radiation. half-dome,, ,then cemented over a The X-radiograph (figure 121 sl~ows mother-&pearl bead of approxi- that they, too, are cultured pearls mately the'same size as the hollow in with lentil-shaped nuclei. The weak tlle dome.,The rest of tlle hollow is fluorescence indicates saltwater then filled with a material that looks origin. We have only enco~~ntered like Canada balsam and a base of such nuclei a few times in the past 30 mother-of-pearl is cemented on. years. We have been told that such As figure 7 shows, the "pearl" on pearls are rare because off-round nu the left appears to be a blister pearl clei in saltwater n~oll~isksincreases still attached to the shell, whereas Figure 8, Flattened freshwater the mortality rate to an unacceptable the one on the right looks like a iin- c~zltureclpearl eu rrings, 18 initi level. isllecl procl~~ct,C.Je;~rly visil>lc in the dioine~er, speciil~enon the right is ;I li~ici)f de- Figure 10. This X-radiograpli 01 ~narcation, w11ich suggests a the pearls in fig~ire8 was taken rnotl~er-of-pearl base (:e~t~cntedto with the pearls 017 edge; it the blister petlrl, Pre[ii~linkirycxan~i- shows their lentil-sliape(1n~~clei nation iriclicatecl that both itz~ns and thus proves their cultured were inlitations, since both had a orjgiti. very low speciiic gravity judging by thei.r h(:ftj tmth felt vety srnooth and warm to the towhi and neither had any orient. Under magnification, some small gas bubbles were visible; in adclitioil, both items were easily inderitecl by the pin point of a brush probe, which suggests that these "pearlst1 were made from xune type of plastic, When we viewed the two Sam- ples with the nlicroscope, we noticed many small bubbles oriented in very closely spaced parallel layerst thus Gem Trade Lab Notes GEMS & GEMOLOGY Sun~~ner1984 109 Fig~~re11. Saltwater cul!:ured pearls seL in earrings, 10 mm in diameter. Figure 13. Note the drilled Figme 14. These surface dimples n~cleusevident in this suggest the presmce of a drill X-radiograph of a 13-mm hole in the nucleus of this cultwed pearl. 13-mm peurl. clcus technique is used in the Mis- quartz cabochons at the Tucson Gem sissippi area. R. C. and Mineral Show held in February of this year. Few of these attractive stones have come to our attention QUARTZ, since we first added the beautiful Figure 12. This X-radiograph of ~nusualliLarge Multi-Star cabochon shown in figure 15 to our one of the pearls in figure 1 1 also Contributing Editor Bob Crown- New York study collection (Gemsel reveals a lentil-shaped nucleus ingshield reports that he was sur- Gemology, Summer 1977). under a thin layer of nacre. prised to see a selection of multi-star Dr. Edward Gobelin studied A third pearl received for testing Figure 15. Multi-star quartz cabochon in the collection of th8 New proved to be a half-drilled freshwater York Gem Trade Laboratory, 22 ct, cultured pearl. The X-radiograph shown in figure 13 revealed that the n~~cleushad been drilled prior to in- sertion in the mollusl<. Evidence of the drilled nucleus shows up in the finished pearl as small depressions on the surface (figure 141. In an article on freshwater pearl cultivation (Gems cd Gemology, Spring 1962)) we learned that round nucleated freshwater pearls were still in the ex- perimental stage at Lake Biwa. Nu- clei insertion in freshwater clams, unlike insertion in saltwater mol- lusks, required special tools which in turn required the drill hole in the nucleus. With a diameter of more than 13 mm, the pearl described here is larger and more attractive than any we have seen before. It may be an American nucleated freshwater cul- tured pearl; however, we do not know whether the same drilled nu- Gem Trade Lab Notes GEMS & GEMOLOGY Summer 1984 several stones from Sri Lanlza to es- an effort to determine if the stone stone was probably heat treated, a tablish that sillimanite inclusions was of Burmese origin. When ex- process known to produce bluish cause the star in that material. How- posed to long-wave ultraviolet radi- fluorescence in ,blue sapphire when ever) we had not encountered any ation) it fluoresced a bright red simi- exposed to short-wave ultraviolet significant commercial offering of lar to that of a Burma stone. How- radiation. The heating could also be these stones until Tucson, 1984. Our ever, with short-wave ultraviolet responsible for the absence of identi- thanks to the New Yorlc gem dealer radiation) a peculiar bluish patchi- fyingsilk in what the dealer assumed who allowed us to photograph the ness and a number of concentric to be a Burma stone. R. c. 170-ct multi-star quartz shown in rings became evident (figures 19 and figures 16 and 17. We are still hoping 201. Because it was suspected that the ruby might have been oiledl the to see a sphere made of this phenom- SAPPHIRE) stone was submitted to the New enal material. R. C. Verneuil Synthetic Yorlz lab. This theory was rejected when it was determined that the blu- Figure 21 illustrates the curved color ish areas did not follow fractures or banding typical of a Vernueil syn- RUBY, Heat Treated rhomboidal 'lbulls-eyell zones. The thetic blue sapphire, In this instance Because Burma rubies fluoresce irregular patch (figure 19) corre- the approximately 5-ct stone, set in a stronger than those from other sponds to a lighter color zone in the ring) had been submitted to the New sourcesl a gem dealer exposed the stone. It was concluded that the Yorlc lab for identification. When the 83.01-ct ruby cabochon shown in stone was viewed through the table, figure 18 to ultraviolet radiation in however, a series of bright parallel ~iiure17. Viewed from a reflection planes were seen (figure different angle, the stone 22).These planes reached the surface Figure 16. Note the sharp star in pictured in figure 16 shows of the table and appeared similar to this 170-ct quartz cabochon. o#her stars. -the surface grain lines in diamond. We could not determine if they were present before the stone was polished and therefore were inherent to the rough material, or if they are the re- sult of some treatment or trauma after cutting. Certainly) they are not typical of synthetic inaterial. Since some heat-treated natural blue sap- phires fluoresce a chalky greenish white siinilar to synthetic stones, a casual examination of this stone after a fluorescence test could mis- Figure 20. Concentric rings were Figure 19. The stone illustrated also evident in the fluorescence in figz~re18 flz~oresceda patchy of the stone in figure 18 when Figure 18. An 83.01-ct ruby blue when exposed to short- exposed to short-wave cabochon. wave uliraviolet radiation. ultraviolet radiation. -- 1 I Gem Trade Lab Notes GEMS & GEMOLOGY Summer 1984 two faceted stones that weighed ap- proxin~ately2 ct each. The client stated that the stones came from a Mexican !tandromediorite" (blaclz metallic ruby). Limited testing again indicated that the faceted stones were probably cut from black spinel. With the permission of the owner, we performed an X-ray diffraction analysis that confirmed our tentative identification: the material was in- deed a variety of spinel and not me- Plgur~21. Curved stri(/e in a Figi1r8 22, U~LZSL~~I~reflection teoritic. I<. H. syr~theticblue sapphir~. planes observed in the stone Magnified 15X. shown in figur~21. Mognifjed 15x. Cat's-eye ZIRCON lead the gemologist if he noted only In this section of the Winter 1983 the reflection planes and not the issue of Gems d Gemology, we fea- curved striae, It is possible that since tured a green cat's-eye zircon that this type of structure has been seen had been brought to the Santa only recently in both New Yorlz and Monica laboratory. Recently! an- Los Angeles) it may be the result of other of these rare stoilest but in a the continuing experimentation different colorl was submitted to our with heat treatment ill gem-cutting New Yorlz lab. Figure 23 shows this centers. R. C. attractive 8.63-ct brownish yellow cat's-eye zircon, with an "eyett equal to that found in fine chrysoberyl. The Pigure 23, An 8.63-ct. brownish stone was easily identified by its typ- Black SPINEL yellow cat's-eye zircon wilh a ical absorption spectrum. Unfortu- In the Gein Trade Lab Notes section fine eye, nately! we have no information on its of the Fall 1982 issue of Gems d country of origin, R. C. Gemology, we mentioned that our New Yorlz labo~atoryhad been aslzed to identify an oval, blaclzt opaque tity could not be verified by means of faceted stone that was supposed to X-ray diffraction since permission have been cut from a portion of a for this test could not be obtained. PHOTO CREDITS Mexican meteorite named "Tile By chancet we recently received Ricardo Cardenas look the photos used in Blaclz Ruby.jt Limited gemological the same material for identification figures 1,3,4,6,16, 17,and21 -23, Shane McClure is responsible for figures 2,5,and testing indicated that the material in our Los Angeles lab. The sample 7. Andrew Quinlan provided figures 8 - 15 was black spinel. However, its iden- consisted of a rough specimen and and 7 8 -20. A PACKAGE DEAL horn GEMS & GEMOLOGY @@@- A complete set of the four information-packed GEMOLOGY for only $3~~00(US.) or $40.00 issues published in 1983 is now available. For (elsewhere). $19.50 (in the US.) or $22.50 (elsewhere),you can To order one or both sets, just send your check have over 250 pages (with more than 200 color or money order to: illustrations) of the most important articles, lab information, and news in gemology today. Back-Issues Department GEMS & GEMOLOGY Or save $4.00 and purchase both the 1982 and 1660 Stewart Street 1983 volumes (eight issues) of GEMS & Santa Monica, CA 90404 Ge~nTrade Lab Notes GEMS & GEMOLOGY Summer 1984 Editorial Forum BRIOLETTE OF INDIA within the past few years. In October 1982) I saw several unusually large, transparent! faceted diaspores. One In my article "Harry Winston: A Story Told in Dia- stone weighed 26 ct and showed a slight color change moncls" [Spring 1983]! I described 14 "namedJJdiamonds from yellow-green to brownish. The largest stone was that Mr. Winston had handled during his career. How- yellow-green and weighed 157 ct. In all, there were about ever) it has recently come to my attention that the 100 pieces available, ranging from 3 to 27 ct, as well as known history of the 90.38-ct Briolette of India) which some rough material. had been reported to be the oldest diamond on record, is not as ancient as many scholars had believed. C. A. Schiffmann, G.G.! F.G.A. Mr. Hans Nadelhoffer, who is compiling a history of Gtibelin Gemmological Laboratory the Carti~r,firin) uncovered some interesting informa- Lucerne, Switzerland tion concerning the true history of this t~nusualstone. During thd course of his research) Mr. Nadelhoffer had the opportunity to interview a 90-year-old Parisian gen- tleman whose father! Atanik Elmayan, ran a very impor- ERRATA tant diamond faceting shop in Neuilly, France, Accord- In the article lllCobalt-blue~Gem Spinelsl!! which ap- ing to the younger Mr. Elcnayan) the Briolette of India peared in the Spring 1984 issue) Mr. Dan Duke was was cut in his father's shop in 1908- 1909. He reinem- inadvertently omitted from the acknowledgments. Mr. bers that the briolette cut was chosen because of the odd Duke loaned several deep-blue natural gem spinels for shape of the original rough. Cartier purchased the stone the study. Also) the last sentence of the abstract for that in 1910, marking the beginning of its verifiable history. article shoulcl readl llFlame-fusion synthetics may still Laurence Krashes be distinguished by their higher R.I.'s." Harry Winston, Inc.! Alsoin the Spring 1984 issue, in the Gem Trade Lab New York Notes section) the natural pearl is thefifth from the right in the bar pin shown in figure 19 (p.49). DIASPORE In the article, "The Rubies of Burma: A review of the Mogok Stone Tractl'(Winter 1983 issue)! the locality Following your published data on a rare 1.24-ct faceted photos in figures 2) 4! 5) and 6 were taken by Dr. Edward diaspore (Gem Trade Lab Notes) Fall 1983)! your readers Gtibelin. might be interested to learn that a deposit of gemmy We apologize for any confusion that these errors and material is said to have been discovered in Turkey omissions may have caused our readers. Editorial Forum GEMS & GEMOLOGY S~~~niner1984 113 GEMOLOGICAL ABSTRACTS Dona M. Dirlam, Editor REVIEW BOARD Mahinda Gunawardene Elise B. Misiorowski Idar-Oberslein, Germany GIA, Santa Monica William E. Boyajian Gary S, Hill Michael P. Roach GIA, Santa Monica GIA, Santa Monica Andin International, New York Jeffrey M, Burbank Steve C. Hofer Gary A. Roskin GIA, Santa Monica Kensinglon, Connecticut Gem Trade Lab, Inc., Los Angeles Stephanie L. Dillon Karin N. Hurwit James E. Shigley San Clemente, California Gem Trade Lab, Inc., Los Angeles GIA, Santa Monica Bob F. Effler Robert C. Kammerling Frances Smith GIA, Santa Monica GIA, Santa Monica GIA, Santa Monica Joseph 0. Gill Neil Letson Carol M. Stockton Gill & Shortell Ltd., San Francisco Anniston, Alabama GIA, Santa Monica Fred L. Gray Shane F. McClure Jill M, Walker Richter's, Nashville Gem Trade Lab., Inc., Los Angeles GIA, Santa Monica COLORED STONES AND Unit-cell parameters are 2 = 15.915 A and = 7.123 A. ORGANIC MATERIALS Because of their negligible iron content, these tourma- Crystal chemistry of tsilaisite (manganese tourmaline) lines have chemical compositions that fall along the from Zambia. K. Schmetzer and H. Bank, Neues solid-solution series between end-member elbaite [ide- Jahrbuch fiir Mineralogie Monatshefte, No. 2, 1984, ally Na(Al,Li],A16B,Si6027(0,0H,F)4]and a hypothetical pp. 61-69. end-member known as "tsilaisitc" [ideally Na(Mn2+]~A16B~Si6027(o,0H,F]4]."Tsilaisite" has not Gem-quality yellow, yellowish brown, and greenish yel- yet been found as a distinct mineral species in nature but low tourmalines from a new occurrence reportedly near has been synthesized in the laboratory. Chipada, Zambia, have manganese contents among the Citing work on manganese tourmalines of Slivko highest ever found in tourmaline group minerals. This (International Geology Review, Vol. 3, 1961, pp. = w = material has refractive indices of 1.622- 1.623, 195 -210], Schmetzer and Bank identify this new natural 1.645- 1.648, birefringence of 0.023-0.025, density of material as "tsilaisite" and report its ideal chemical about 3.13 ~/cm~,and MnO content of 6.37-6.80 wt%. formula as Na [~nf$A~~.~]A~~B~s~~o~o~.~(oH,F]~.~. However, they give no indication that this usage has been formally approved by the Commission on New This section is designed to provide as complete a record as Mineral Names of the International Mineralogical As- possible of the recent literature on gems and gemology. Articles sociation, which is the normal procedure for new min- are selected for abstracting solely at the discretion of the section eral descriptions. The authors discuss possible isomor- editor and her reviewers, and space limitations may require that we include only those articles that will be of greatest interest to our phic replacement mechanisms along the elbaite- readership. "tsilaisite" solid-solution series. These mechanisms Inquiries for reprints of articles abstracted must be addressed to appear to involve the two reactions Li+ + (OH]= Mn2+ the author or publisher of the original material. + 02-and, to a lesser extent, A13+ + 02"= Mn2+ + The reviewer of each article is identified by his or her initials at the (OH)". When combined, these reactions give Li+ + A13+ end of each abstract. Guest reviewers are identified by their full = 2Mn2+.The extent to which this substitutional mech- names. anism is compatible with the crystal structure of tour- 01984 Gemological Institute of America maline is presently unknown but under investigation. IES 114 Gemological Abstracts GEMS & GEMOLOGY Summer 1984 The geochemistry of beryllium and fluorine in the gem identification of five new color centers not previously fields of Sri Lanka. M. S. Rupasinghe, A.Banerjee, C. recognized. In citrine, the new centers are similar to Dissanayke, and J. Pense, Mineralium Deposita, those long suspected to be the cause of color in smoky Vol. 19, No. 1, 1984, pp. 86-93. quartz. They seem to involve the oxygen atoms that are Sri Lanka has long been an important source of various adjacent to either aluminum or other atoms that are gemstones, including corundum, chrysoberyl, beryl, substituting for silicon in the quartz crystal structure. garnet, spinel, tourmaline, and topaz. The island is Details of the nature of these individual centers are primarily composed of a series of crystalline metamor- presented. !Es phic rocks andpegmatites of Precambrian age. Most gem minerals are not found in situ, but rather occur as part of heavy-mineral placer deposits in sediment gravels de- DIAMONDS rived from the erosion of these underlying crystalline Cathodoluminescence of natural diamond associated rocks. This particular study focuses on the geochemical with implanted impurities (in Russian]. V. S. Vav- behavior of beryllium and fluorine in this sedimentary ilov, A. A. Gippius, V. A. Dravin, A. M. Zajccv, and weathering environment and on their role in the forma- B. S. Zakupbekov, Soviet Physics of Semiconduc- tion of gem deposits. Beryllium is an important constit- tors, Vol. 16, No. 11, 1982, pp. 1288-1290. uent of beryl and chrysoberyl, while fluorine occurs in This article, by a team of Soviet researchers from the tourmaline and topaz. Lebedev Physics Institute of Moscow, provides help in Although fluorine and beryllium have a common understanding the role of specific impurities in the phys- origin in pegmatites, the results of this study demon- ical constants displayed by both natural and synthetic strate that they behave differently during the subse- diamond. The information provided may further be use- quent erosional cycle and are not concentrated in the ful in developing quick techniques for distinguishing same minerals in gem sediments. This study is one of the two, should this become necessary on a commercial the first detailed investigations of the geochemistry of level. the gem sediments of Sri Lanka, and points the way to a The authors note that nitrogen in diamond has al- better udderstanding of gemstones in 'such environ- ready been singled out as playing the dominant role in ments in the earth's crust. IES optical properties such as absorption and luminescence. The latter phenomenon has also been associated with Identifying turquoise. G. Brown, Australian Gem- traces of silicon. In their experiments the writers mologist, Vol. 15, No. 3, 1983, pp. 289-299. "doped," or implanted, relatively pure natural diamonds Brown divides "turquoise" into five categories and dis- of the IIa type with ions of some nine metallic elements cusses methods of identifying each. The first is natural in order to observe any distinctive effects on the turquoise. The second, impregnated turquoise, is sub- cathodoluminescent spectra of the stones. The depth to divided into three types: Paraffin wax and thermosetting which bombardment by the accelerator managed to resin impregnation are both identified by use of the penetrate the diamonds was also studied, by etching microscope and hot point; sodium silicate impregnation away layers as thin as 200 A (one fifty-thousandth of a is indicated when a drop of ammoniacal silver chromate millimeter) and checking for evidence of centers of solution produces a reddish brown spot. luminescence. Stones in the third category, imitation turquoise, Typical of the results obtained are some observa- are identified by normal gemological properties with the tions on the nature of nickel impurities introduced into exception of reconstructed turquoise; a drop of hydro- the natural stones. Synthetic diamonds often display a chloric acid on the surface of a reconstructed turquoise triplet of lines in their spectra around 484 nin (at 484, leaves a yellow spot. Next, the characteristic surface 489, and 491 nm] and a single line at 510 nmj these are patterning of synthetic turquoise is magnified to obtain caused by nickel contamination from the catalyst used an identification. Stones in the last category, naturally to help manufacture the crystals. According to the au- occurring turquoise simulants, can be identified with thors. these lines have never been observed in natural the usual gemological tests. GSH diamonds-but were successfully induced during the course of the experiment in those natural diamonds New hole centers in natural quartz. D. Maschmeyer and implanted with the nickel ion. G. Lehmann, Physics and Chemistry of Minerals, Similar results for other elements are discussed, Vol. 10, No. 2, 1983, pp. 84-88. demonstrating the usefulness of luminescent spectra in Atomic-level structural defects known as color centers synthetic detection. We may also speculate that a are responsible for the coloration of certain gem mate- knowledge of how to induce spectral lines previously rials. Such is the case in some varieties of natural quartz. restricted to synthetics could lead to methods of obscur- Electron paramagnetic resonance (EPR] measurements ing these same lines, giving gemologists yet another of several citrines from Madagascar have led to the challenge in identification. MPR Gemological Abstracts GEMS & GEMOLOGY Summer 1984 115 DeBeers returns tozaire. Indiaqua, Vol. 35, No. 2, tacular initial success six years ago. He traces the for- 1983, pp. 11- 14. tunes of two companies, Theron Holdings and Trans- This article begins with a quote from a statement issued Hex, both active in the Atlantic Ocean off the west coast by the chairman of Dc Beers on April 27, 1983, to the of southern Africa. effect that the "Governn~entof Zaire has recently judged In 1978, Theron Holdings formed a subsidiary com- it to be in the best interest to renew its old-established pany, Dawn Diamonds, which was partly financed by an relationship with us." Using excerpts from six news overseas consortium that included Swiss oceanographer items, this discussion goes on to argue that one factor Jacques Piccard. Dawn Diamonds obtained rights to influencing Zaire was the decision by Australia to mine diamonds from Terra-Marina, a subsidiary of market the majority of the diamonds from the Argyle Trans-Hex. operations through De Beers. Zaire will, undoubtedly, From 1979 to 1983, Dawn Diamonds produced an be better off not having to compete with these diamonds average of 22,000 ct annually from gravels recovered by as an independent. divers using suction hoses. Some of the early profits Production of alluvial diamonds will continue out- were reinvested as the company expanded and diversi- side De Beers control. To combat smuggling, the Zaire fied. Thcn, in 1981, not only did diamond prices fall, but government now allows independents to set up buying the concentration of diamonds in gravels also dropped offices near alluvial areas. One such group, Harry significantly from a high of 18 ct per cubic meter to a low Winston, lnc., reportedly paid $1 10,000 to the govern- of 3 ct. ment for the permit. Among the 11 photographs are Gurney emphasizes the difficulties encountered in examples of both the alluvial and hard-rock mining. mining at sea as he describes the financial upheavals of DMD these two companies. He concludes with a short dis- cussion of recent changes in the leasing program for Guinea diamond project on schedule. Mining Journal, rights to offshore mining. Since 1970, the Department Vol. 301, No. 7740, 1983, pp. 451-452. of Mineral and Energy Affairs of the Republic of South Diamonds-Aredor update. Mining Journal, Vol. Africa has issued two-year leases to the western coast 302, No. 7744, 1984, p. 36, area. In July of 1983, these leases were further subdi- Mining Journal reports on the progress of the Aredor vided into near shore, middle, and deep water. Gurney alluvial mining project in Guinea, West Africa. The speculates that, with the new leases, opportunities Aredor plant, located at Kerouane, near the Sierra Leone abound, and the prospects for these two companies are border, contains a recovery facility with heavy media promising. DMD separation, washing, and feed sections, as well as a sepa- rator house. With treatment of the first diainond-bearine- Zoned garnets in porphyroblast lherzolites from the Mir gravels expected this year, the partners of the project kimberlite pipe (in Russian). V. P. Serenko, K.N. predict an initial output of 250,000 ct/yr. Information Nikinov, and E. E. Laz'ko, Dolzlcidy Alzadeinii gained by prospecting suggests that 90% of the dia- Naiik SSSR, Vol. 267, No. 2, 1982, pp. 438-441. monds are gem quality, with an average stone size of Zoned garnets in a xenolith of cataclastic peridotite 0.53 ct. If production follows the prospecting prediction, from the Udachnaya kimberlite pipe in Yakutia (in there should be sufficient gravel for 16 years of plant Russian]. E. E. Laz'ko, V. P. Serenko, and G. N. operation. Muravickaja, Doklady Akademii Nauk SSSR, Vol. Sierra Leone geologists located the Guinea deposits 268, No. 5, pp. 1204- 1208. in 1932. While these were worked by Selection Trust Garnets are often found in association with diamonds in (the company working the alluvial deposits in Sierra kimberlite pipes, a phenomenon exploited to great ad- Leone) and by the Soviet Union in the late 1960s this is vantage by those searching for such treasures. The rich the first large-scale, fully mechanized mining operation. Orapa pipe of Botswana, for example, was located by De Included in the update are further details about the cor- Beers geologists far below the overlying sands of the porate holdings of Aredor Holdings Ltd., as well as ex- Kalahari Desert using indicators such as garnet particles pansion plans. The rough will be distributed through carried to the surface by ants. As reported in this pair of Jack Lunzer's Industrial Diamond Company. In the long articles, Soviet researchers investigated garnets from term, there may be potential for hard-rock mining, since two of the major Russian pipes in order to gain clues not 19 kimberlite pipes are known to exist within the only to how diamond appears in the kimberlite, but also Aredor lease area. DMD to the geologic processes taking place in the upper man- tle of the earth itself. Sea diamond developments. J. J. Gurney, Indiaqua, Vol. The garnet samples studied were purposely taken 36, NO.3, 1983, pp. 13-17. from rocks within the kimberlite that are known to form In an interesting update, Gurney summarizes the devel- at great depth: from lherzolites found in the Mir pipe of opments in the sea mining of diamonds since its spec- the Malo-Botuobinsky kimberlite field and from a cata- 116 Gemological Abstracts GEMS & GEMOLOGY Summer 1984 clastic peridotite derived from the Udachnaya pipe of gamma ray emission (PlGE),are discussed in this article. the Daklynsky field. Pyrope and almandine were the Both methods involve the exposure of an item to a high- most common species encountered, with grossularite, energy beam of protons which gives rise to characteristic andradite, and uvarovite also represented. X-ray or gamma-ray emission of energy that can be de- Variations in both color and chemical content ac- tected with suitable equipment. Analysis of this energy cording to the location of the garnets in the rock were emission can provide an indication of the chemical ele- analyzed and are compared in detailed tables and graphs. ments in an item, as well as their abundance. The The authors interpret these results to indicate that the practical application of these techniques to determine garnets formed by diffusion inetasomatism (mineral re- the origin of soldering and brazing compounds used in placement), during a drop in pressure and rise in temper- the manufacture of gold jewelry is described. ature, below the layers of sedimentary rocks through The presence of cadmium (Cd)in soldering alloys which the diamond-bearing kimberlites later were in- has often been interpreted as identifying an object as jected. MPR being of modern origin because this element has only been known since the early 1800s. However, recent PIXE analyses of several ancient, soldered gold objects INSTRUMENTS AND TECHNIQUES found to contain small amounts of cadmium have cast Advances in the study of mineral inclusions. G. Gra- some doubt on this hypothesis. The cadmium contents ziani, Neues Jahrbuch fur Minerdogie Monat- of these ancient alloys apparently resulted from the mix- shefte, No. 11, 1983, pp. 481-488. ing in small quantities of the mineral greenockite, a In this article, Professor Graziani describes his ingen- naturally occurring cadmium sulphide, in the alloy ma- ious and unique method of extracting the contents of terial to lower its melting point. Thus, while the mere fluid inclusions for analysis by Gandolfi X-ray camera presence of cadmium does not establish the age of an and/or an electron probe microanalyzer. The method artifact, comparison of the proportions of cadmium to utilizes an original microtechnique called "microscopic other alloy elements, such as copper or silver, does pro- extracting assemblage" (MEA). vide a more reliable indicator of origin. For solder alloys The required apparatus consists of (1) an inverted in ancient jewelry, there is a mutual increase in both microscope modified for mineralogical observation and cadmium and copper contents, whereas for modern photomicrography; (2)a dental microdrill, with a motor times an inverse correlation is observed in which the speed ranging from 1,500 to 30,000 r.p.m., that can be copper/silver content decreases as the cadmium content used in a vertical or horizontal position and employs a is increased. These analytical techniques offer a rapid variety of small diamond tools; (3)a simplified, liquid and accurate means of determining the element com- nitrogen-based, gas flow freezing stage system to freeze position of jewelry. As the methods are further refined the inclusions and control heat build-up during drilling with the analyses of additional objects, they will provide (the positioning of the inverted microscope also allows an important tool for examining ancient jewelry arti- the drilling tool to be cooled down during use); (4) a facts. JES Leitz-type micromanipulator to control the sample dur- ing extraction, and (5) a chrome1 vs. alumel X-ray unit for gemmological use. S. Folgueras- thermocouple-potentiometer assembly for accurate Dominguez, Journal of Gemmology, Vol. 19, No. 1, temperature measurement during the extraction pro- 1984, pp. 14-23. cess. Transparency to, and lun~inescenceexcitation by, Using Professor Graziani's MEA technique, the mi- X-rays are two advanced techniques used in gemstone croscopist can locate fluid inclusions, define the optical identification. This article describes the operation of a properties of both the inclusions and the host crystal, simple, portable X-ray unit for documenting the relative and extract the contents of the inclusions for analysis X-ray transparency of gem materials. The degree to without having to move the specimen and while keep- which a material will absorb a beam of X-rays depends ing it at a desired constant temperature. The MEA on the thickness of the material and the nature of its method is quite intriguing and should prove helpful to constituent atoms. For a given thickness, there is a inclusionologists worldwide. John I. Koivula marked difference in relative X-ray transparency from one gem material to the next. The author illustrates this Analysis of gold jewellery artifacts-characterization of difference with a table of diamond and possible diamond ancient gold solders by PIXE. G. Demortier, Gold simulants in which this transparency is shown to vary Bulletin, Vol. 17, No. 1, 1984, pp. 27-38. by a factor of lo6 or more. The differentiation of various New, sophisticated, nondestructive analytical tech- gem materials by this method becomes even more pro- niques are beginning to be used to establish the antiq- nounced as the thickness of the gemstone increases be- uity of jewelry artifacts. Two such techniques, particle- cause of the greater degree of X-ray absorption. induced X-ray emission (PIXE) and particle-induced The portable unit consists of anX-ray tube mounted Gemological Abstracts GEMS & GEMOLOGY Summer 1984 117 in a shielded box with windows that allow for direct imperial regalia from the time of Charlemagne to the observation of either thex-ray transparency by means of present day. Readers will be surprised by the number of a mirror or the X-ray fluorescence and phosphorescence ancient crowns still surviving and the extraordinary of a gemstone. The brief exposure time, on the order of lack of precise information about them. The crowns, one second, appears to be insufficient to produce color orbs, scepters-"indispensable instruments of changes in the gemstone being examined. The unit can coronation1'-are seldom used in the 20th century, yet also be used to obtain radiographs of pearls. As with all they seem to have more prestige now than in former X-ray equipment, caution must be exercised during its times and continue to serve as emblems of national, if operation. Check that the equipment is properly not personal, sovereignty. shielded so that the X-rays are completely contained Prince Michael provides some surprising and curi- within the unit. In addition, an approved operator's li- ous anecdotes, but adds little new information to cense from local health authorities would be required. knowledge of the subject. Considering his relationship IES to two royal houses, more previously unpublished ma- terial might have been expected. His research lacks ob- JEWELRY ARTS jectivity, and he has allowed some serious errors in fact The art of Faberg6. B. Foran, Robb Report, Vol. 7,No. 12, that appeared in the book to carry over into the article. 1983, pp. 104-1 13. The article is aimed at a wide public, and while Just when it seems that everything that can be written serious jewelry historians may be disappointed, the pho- about Faberg6 has been written, along comes an article tographs serve as some compensation. Hopefully, the with a new perspective, offering practical information to book and the present adaptation will encourage more the Faberg6 enthusiast. scholarly consideration of a subject which has almost Since the Robb Report specializes in investment unlimited potential. NL advice, it follows that this aspect of Fabergk collecting is emphasized. Oddly enough, the escalating prices and Enameling-I: Introduction and cutting cells for profit potential of these exquisitely crafted objects are Champlev6 enamelling. C. Walton, Aurum, No. 16, often obscured by the romantic aura surrounding the 1983, pp. 33-41. legendary firm of Russian goldsmiths and its enigmatic This is an interesting, though not particularly informa- founders. While this article does dwell on the history of tive, article. The subtitle, "Introduction and Cutting Faberge, it also provides useful information on the value Cells for Champlev6 Enamelling," promises more than of these collcctibles. the article delivers. The "Introduction" consists of a Writing for a general but presumably informed au- short professional biography of three members of a Lon- dience, the author reviews the life and times of Peter don enameling firm along with their accomplishments, Carl Faberg6, detailing the rise of the firm in St. a hazy definition of enamel, a brief description of each of Petersburg and recalling the glittering list of interna- the four basic raw enamels, and an esoteric mention of tional society, royalty, and just plain rich who patron- the techniques behind four of the main types of ized his shops in Russia and the branches in London, enameling. Paris, and Monte Carlo from the late 19th century to the The discussion concerning cell preparation for Bolshevik revolution and the fall of the Romanov dy- Champlev6 enameling is only a bit more informative. nasty. Interesting anecdotes on prominent Faberg6 col- Section headings would have the reader believe that lectors (notably, publisher Malcolm Forbes),a short list there will be insights into the process, but attention is of current and forthcoming publications on the subject, given to the difficulty of execution rather than to the and information on permanent Fabergk exhibitions are process itself. illustrated with representative but infrequently pub- The photographic essay accompanying the article is lished Faberg6 objects. The Robb Report and author more informative and valuable than the text. The article Barbara Foran have presented a fresh, readable article to does, however, serve to whet the appetite, and the prom- wind up a year in which Faberg6 became a household ise of a follow-up article leaves hope of real information word and two major exhibitions of his work were held in to come. Archie V. Ciirtis America. NL Gold coins as jewellery through the ages. A. Oddy, Crowningglories: sumptuous jewels of dynastic Europe. Aurum, No. 15, 1983, pp. 10-16. Prince Michael of Greece, Smithsonian, Vol. 14, The current vogue of incorporating gold coins in jewelry NO. 7, 1983, pp. 129-141. undoubtedly prompted this article on the early use of Despite the cumbersome title, this is a splendidly illus- gold coins for adornment. Concentrating primarily on trated article adapted from Prince Michael's Crown the Roman and Byzantine periods, the author shows the fewels of Europe, published late last year by Harper & influence of politics and religion on the fashion of wear- Row. The article traces the use and variety of royal and ing coins. Although coinage was invented in the late 118 Gemological Abstracts GEMS & GEMOLOGY Summer 1984 seventh century B.C., it was not until the second century University. This issue of Arts of Asia focuses on the A.D. that the Romans first used coins in jewelry. By this various collections at this institution. time, the minting of coins had been standardized and all The first half of the article presents a terse history of coins were stamped with the head or bust of the em- stone seals in the Near East up to the introduction of the peror. Wearing his image denoted support of the ruler, cylinder seal. The stamp seal, which first appeared in and some of the earliest examples of brooches and pen- northern Mesopotamia around 5000 B.C., served as both dants may have been made as gifts for foreign ambassa- art and a device for sealing. Around 3000 B.C., in the dors or citizens favored by the emperor. "Coin" jewelry Tigris-Euphrates River plain, there appeared a different, also appeared in the form of bracteates, or thin sheets of distinct type-the cylinder seal. For the cultures of gold stamped out using coins as dies. These bracteates Sumer, Babylon, and Assyria, the cylinder seal achieved were often grouped together to form necklaces and the status of a major art form, although its primary wreaths for the hair. In light of their fragility, Oddy purpose was to serve as a means of applying a signature suggests that bracteate jewelry may have been made by rolling the cylinder over clay or some other impres- specifically for funereal use. sionable substance. The earlier cylinder seals were made We see the decline of the Roman Empire and the rise of soft stone, such as limestone, but later such materials of the Byzantine Empire in the use of coins from various as hematite and the variously colored quartzes were barbarian kingdoms that replaced former Roman prov- more commonly used inces, as well as in coins from Byzantium set in garnet The second half of the article describes six examples and gold mounts. As Christianity spread through of individual cylinder seals in the Oriental Museum Europe, the practice of burying goods with the dead was collection. Six photographs of impressions of the seals discontinued, so that fewer pieces of coin jewelery have accompany an interesting text. The article concludes survived from this period than from earlier ones. One of with a reference to a more complete discussion of the the survivors is a neck ring made up of coins and medal- collection. FLG lions that span the fourth to sixth centuries. The author speculates that this may have been a m'aniakion, the Southern collections: jeweled bibelots in the Headley- badge ofoffice worn by the Byzantine imperial guard during the sixth century. Whitney Museum. N. Letson, Southern ~ccents, Although gold coins were minted from the fifth to Vol. 6, No. 1, 1983, pp. 34-40. the 14th centuries by the Byzantine Empire, virtually no Located in Lexington, Kentucky, the Headley-Whitney gold was minted in the rest of Europe from the seventh Museum was founded in 1968 by George W. Headley and until the 13th century. Coins introduced at this time his late wife, Barbara Whitney Headley. The museum were often inscribed with religious phrases and were offers changing exhibits of art, Oriental porcelains, a worn as amulets to protect travelers. large collection of rare shells and fossils, and the largest Oddy then speeds us through the subsequent cen- contemporary collection of jeweled bibelots (small turies to the present day in two paragraphs, informing us household curios or trinkets) in the United States. that coins in jewelry were prevalent, especially in the These bibelots are housed in the Jewel Room, one of the 19th century, due to a revival of interest in the classical standing exhibits at the museum. Both the Jewel Room age, and that examples of these can still be found in and many of the objets dfart it contains were designed antique shops. EBM by George Headley and represent his taste and discern- ment in the assemblage of rare and unusual treasures. Precious time. T. N. Murari, Connoisseur, Vol. 213, No. Fabricated by leading craftsmen of this century 861, 1983, pp. 106-111. from detailed water-color designs by Headley, these cu- A small group of jeweled watches, "The Ermitage Col- rios incorporate gems and precious metals with natural lection," by Piaget of Geneva, will tour the United materials and antiques. Branch coral, volcanic rock, States in 1984. The watches resemble in style the Art petrified wood, and rhinoceros horn as well as existing Deco watches of the early 20th century. T. N. Murari, a sculptures, antique coins, and carved jade and ivory are novelist, has written more of an advertisement than an some of the materials used, all of which were collected essay; nevertheless, the illustrations and some of the by Mr. Headley on his travels around the world. verbal descriptions make the article worthwhile. One of the outstanding pieces described in this ar- JG/FS ticle is a miniature classical temple made by Bulgari of Rome. The temple, constructed of 18-karat gold, frosted Some ancient Near Eastern sea1s.W. G. Lambert, Arts of rock crystal, and diamonds, is seated on a large natural Asia, Vol. 18, No. 6, 1983, pp. 84-86. crystal from Brazil. In part because of its imperialistic past, Great Britain is From the author's descriptions of the Headley- very rich in Eastern antiquities. Lambert describes an Whitney, one gets the feeling that the entire museum is English collection of Eastern seals that is housed in the a jeweled ornament, fascinating and beautiful in its de- rather obscure Oriental Museum located at the Durham sign and execution., EBM Gemological Abstracts GEMS & GEMOLOGY Summer 1984 119 SYNTHETICS AND SIMULANTS with violet to red play-of-color)-no distinct water con- tent; sample 3 (black body color with violet to blue Gilson created fire opal imitation with play of colours. play-of-color)-presence of at least one organic com- M. Gunawardene and R. Mertens, journal of Gem- pound; sample 4 (black body color with violet to red mology, Vol. 19, No. 1, 1984, pp. 43-53. play-of-color)-presence of at least one organic com- This article reports on the examination of a Gilson pound; sample 5 (yellowish brown body color with vio- product variously described by the producer as "Mexi- let to red play-of-color, resembling fire opal)-no dis- can fire opal-type synthetic" or "synthetic honey tinct water content, presence of 16% organic com- opal." The properties of this material were determined pounds. to be as follows: (1) General appearance-distinct yel- The investigator concludes that, on the basis of the lowish brown body color with a pronounced play-of- above examination results, all five products are more color; a predominance of reddish flashes was noted, par- properly designated opal imitations than synthetic opal. ticularly in one specimen. (2)Refractive index = 1.41 & R CK 0.001, and specific gravity = 1.91  0.001. (3)There is an affinity for water (hydrophilic),but it is much less than Large crystal sapphire optics. F. Schmid and C. P. Khat- previously reported for Gilson black opal and white opal ta k, Laser Focus/Electro-Optics, September 1983, simulants. (4)"Feel" test-feels rough to the moistened pp. 147-152. thumb (natural honey opal reportedly feels smooth).(5) Ultraviolet fluorescence-inert or distinct bluish white; This article reports on a new crystal-growing technique those specimens that fluoresced also phosphoresced, known as the Heat Exchanger Method [HEMTM).The with reactions stronger to long-wave than to short-wave HEMTMprocess is the only melt process that uses a radiation; further, those specimens that fluoresced also vacuum in which to grow crystals. During crystal exhibited a strong, chalky bluish white thermolumines- growth, a seed is placed at the bottom of the crucible and cence at 30° to 40°C prevented from melting by starting a flow of gaseous Microscopic examination using transmitted high- helium through the heat exchanger. This lowers the intensity fiber-optic illumination revealed a temperature of both the heat exchanger seat and the seed "chicken-wire" pattern. A number of additional charac- crystal resting on it. Crystal growth then takes place teristics were noted under lower-intensity lighting from the seed outward. This method has produced conditions, including the characteristic "lizard skin" large-diameter (up to eight inches or so) synthetic color- or "fish-scale" effect previously noted in the Gilson less sapphires that are free of the light-scattering bits black materials and white materials, as well as dendritic that generally occur in the boules grown by the Verneuil patterns reminiscent of those seen on moss agate. Exam- or Czochralski processes. ination at oblique angles revealed a dangling "stalacti- Scatter-free sapphire slices make very effective tic" color distribution; when the Gilson stone was windows for detectors in satellites. Synthetic ruby and viewed from the side, substructural boundaries to the titanium-doped sapphire have also been grown by color columns were noted. HEMTMfor laser research. The process allows an in-situ The article is accompanied by seven annealing of the solidification stresses, and thus can photomicrographs and two drawings illustrating these make large-size crystals without stress-related cracking. structural features. RCK Efforts are now under way to grow Cc:Mg and Nd:YAG crystals by HEMTM. BFE An investigation of the synthetic products of Gilson showing a play of colours. K. Schmetzer, journal of Gemmology, Vol. 19, No. 1, 1984, pp. 27-41. MISCELLANEOUS The recent introduction of a Gilson product resembling fire opal with play-of-color led the investigator to thor- Mammoth unearthed. D. Hemenway, Earth Science, oughly examine a number of different Gilson materials Vol. 36, No. 3, 1983, pp. 16-17. marketed as synthetic opal. Five basic sample types To comply with the restrictions on ivory included in the were evaluated using X-ray powder diffraction, ther- Endangered Species Act, some lapidaries have substi- mogravimetry, chemical analysis, flame ionization tuted fossil ivory. One form used is the tusks of woolly analysis, and mass spectrometry. mammoths. Hemenway presents insight into the Results of these investigations showed significant lifestyle of Mammuthus primigenius, one of the woolly differences in the chemical composition of these man- mammoth species that lived in Siberia. made materials as compared to natural gem-quality In terms of size, the mammoth is between the larger opal. The five basic sample types and the major differ- African elephant and the smaller Asian elephant. How- ences noted are as follows: sample 1 [white body color ever, mammoth tusks are the largest of all the elephants, with violet to green play-of-color)-no distinct water weighing up to 120 kg and reaching lengths of 3 to 4 m. content, presence of crystalline Zr02 (supposedly pro- The author concludes this well-written article with ducing the white body color); sample 2 (gray body color accounts of discoveries of mammoth fossils. DMD 120 Gemological Abstracts GEMS & GEMOLOGY Summer 1984 John I. Koivula, Editor DIAMONDS from a locality in Rhode Island that was previously Brazil thought to be exhausted. The deposit is situated along Large diamond found in Brazil. A 260-ct yellow dia- the shores of Narragansett Bay near the Bristol-Mount mond of stated "good quality" was recently found at Hope Bridge area. Mr. Stevens has found gem crystals as Coromandel (about 300 lzm northwest of Belo Hori- large as 100 ct. zonte) in Minas Gerais, Brazil, by a local garimpeiro. This area has produced many fine diamonds over the Exploration in Zambia. The International Development years. Perhaps this discovery will spawn a more organ- and Construction Company of Saudi Arabia and the ized and detailed exploration of the area than has been Reserved Minerals Corporation have reportedly joined carried out in the past. forces to recruit qualified mining personnel to prospect for and mine emeralds and other precious minerals in India Zambia. Diamond exploration. The Mineral Exploration Corpo- ration and the National Mineral Development Corpo- New mining policy in Tanzania. The Tanzanian gov- ration, with cooperation from the Geological Survey of ernment is preparing a new mining policy that will af- India, are implementing the first phase of a nationwide fect small mining operations. The new policy will allow diamond exploration program. The first area targeted is individuals, groups or even entire villages to prospect for Andhra Pradesh. Diamonds have already been found and and mine diamonds, colored stones, gold, and other pilot plants have been constructed. minerals on a small scale with minimal government interference. Philippines First diamond-cutting factory in Philippines. A New source for beryllium. Highwood Resources Ltd. has diamond-cutting factory has now been set up in the encountered significant concentrations of beryllium Philippines near Manila. The company, called Manila during drilling operations at their Thor Lake property, Gem Polishers, is jointly owned by an Israeli, Mr. Y. North West Territories, Canada. Values as high as Goldenberg, and a Philippine, Mr. Antonio Marco. The 2.38% beryllium oxide have been reported, and plans factory is presently cutting only small (1-50 points], now exist to perform a feasibility study on the prospect. lower-quality goods. Although the beryllium found at this locality has not been in association with gem materials, whenever be- Singapore ryllium is found in a mining area the potential for Diamond exchange. The Singapore Diamond In~porters beryllium-containing gem crystals exists. Such Association recently announced that its new diamond localities are always exciting sites for gemological exchange will be operational by the middle of 1984. The prospecting. exchange, which is already affiliated with the world federation, will have approximately 200 members and New York chrysoberyl. Mr. Clifford Stevens also reports will be the first such exchange in Southeast Asia. of reworking an old Dana locality for chrysoberyl in his home state of New York near Greenfield. In Gemstones COLORED STONES of North America (Sinlzanlzas, 1976), this locality is Activity in Pakistan. The Gemstone Corporation of listed as being located "immediately west of a small Pakistan reports that three new emerald deposits have pond just north of the township road which crosses been found in Charbagh, Gujar Killi, and Makad. As a Highway 9 leading north from Saratoga. The pond is by-product of initial exploration, 11,728 ct of rough em- about one-half mile west of the intersection of the town- eralds have been recovered. Opened in 1981, the aqua- ship road with Highway 9.'' marine and beryl deposits in Dassu (Slcardu) and the Many small crystals (up to 1.5 cm) displaying the topaz deposits in Katlang (Mardan)continue to produce typical wedge-shaped twin habit have been found. They consistently. are greenish yellow and mostly translucent. Amethyst from Rhode Island. Mr. Clifford H. Stevens, Recent finds in Yugoslavia. Gemologically interesting a gemologist from Gansevoort, New York, reports that deposits of the silica gems opal, chalcedony, and jasper he has rediscovered a deposit of gem-quality amethyst have been discovered in Serbia, Yugoslavia, on the Gem News GEMS & GEMOLOGY Summer 1984 121 slopes of Mount Rudnik. Whether or not mining of these Holloway and Harker townships. Initial drilling has deposits will be economically feasible remains to be begun on the property to determine the extent of the seen. mineralized structure and to test any extensions of the main zone. Preliminary testing of the area is scheduled PRECIOUS METALS to be completed in 1984. Canadian gold. The Canadian gold producer, Lac Min- erals, has reported that recent drilling activity on its OK gold. Production at the giant OK gold mine located Williams gold property at Hemlo, in Ontario, has up- in Papua, New Guinea, may begin sometime this year. graded the previous estimate of reserves for the property However, some serious problems with mud slides will from 10.0 million tons at 5.8 g (0.18 02.) of gold per ton of increase the recovery costs for the gold. ore to 13.9 million tons at 5.9 g of gold per ton. This is in addition to3.5 million tons of near-surface ore with gold Reid mine. Exploratory drilling at Terramar Resource Corporation's Reid mine in northern California has re- values grading at 6.2 g (0.1902.1 per ton. The Hemlo area promises to be one of the most important sources of gold vealed gold values as high as 46.9 g (1.50 oz.] per ton. A in the world. Production at Hemlo could begin in 1984. section extending vertically from 7 m to 43 m showed a weighted average of 21.6 g (0.69 02.) per ton of ore and Gold in Quebec. A strata-bound gold-bearing zone has 50.4 g (1.62 02.) per ton of silver. Another section, ex- been found by Camflo Mines about 65 km north of tending from 57 m to 59 m, showed 12.3 g of gold and Kirkland Lake, Quebec, Canada, on its property in the silver values of 19.9 g per ton. Winner of the 1984 George A. tions will be available at that time P.O. Box 51, Short Hills, NJ07078; or Schuetz Memorial Fund Design from the Scholarship Office, Elna Hauck, 8 Rowe PI., Bloomfield, Contest is Mr. Sekikazu G. Nakak- Gemological Institute of America, NJ 07003. ura, of Okayama-City, Japan, for his 1660 Stewart St., Santa Monica, CA original design of a 14K white-gold 90404. The International Exhibition of and yellow-gold man's bracelet (fig- Jewelry, Gold, Silverware, Clocks, and Gifts ("BIJORHCA") will be ure 1). Other winners in the design The Geo-Literary Society was competition were Mrs. Shizuyo held September 7- 12, at Parcdes Ex- formed at Tucson in February of this positions, Porte de Versailles, Paris. Hara, of Tokyo, Japan, in second year. Mrs. Alexandra Filer, of Filer's Further information and entrance place, and Ms. Catherine D. Vil- Minerals, has been elected the first cards are available from: Pierre lenueve, of Montreal, Quebec, Can- president. The Geo-Literary Society Wagner and Caline Thomas, Inter- ada, in third place. has an initial goal of bringing to- national Trade Exhibitions in The Schuetz contest, held annually, gether those who are interested in France, Inc., 8 West 40th St., New awards scholarships in the amounts the literary arts related to minerals, York, NY 10018; (212) 869-1720. of $500 for first place, $300 for sec- gems, and fossils. The sharing of ond place, and $200for third place for sources and the exchange of infor- You are cordially invited to attend training in a jewelry-related subject mation about books, maps, draw- GIA GemFest '84, a program of senl- at any institution of the winner's ings, and related printed matter on inars specifically designed to in- choice. Only original designs of the subject of the natural substances crease your jewelry sales ability and men's jewelry are eligible for entry in of the earth is of prime concern to the gem knowledge, to be held August 21 the competition. The 1985 Schuetz group. For further information, con- and 22 at CIA Santa Monica. Please contest will be open in October of tact: Filer's Minerals, Box 487, call GemFest at (213) 829-2991 for this year. Contest rules and applica- Yucaipa, CA 92399; or Herb Obodda, further information. Figure 1. Schuetz award-winning bracelet design by Sekikazu G. Nakakura. Gem News GEMS & GEMOLOGY Summer 1984 THE PHYSICS AND that accommodates many different CHEMISTRY OF COLOR interests. By Kurt Nassau, 454 pp., illus., publ. Numerous line drawings, dia- by John Wiley a) Sons, New York, BOOK grams, graphs, and assorted tables appear throughout the book. Eight As the title suggests, this book delves pages with 31 color photos are into the fundamental processes that sandwiched in the middle of the text produce or alter the patterns of visi- REVIEWS and provide some beautiful illustra- ble radiation that are perceived as Michael Ross, Editor tions. There are also 11 blaclz-and- color. The author, a research scien- white photos scattered throughout. tist at Bell Laboratories, has added The greatest value of the book, how- The Fifteen Causes of Color as a ever, is the amount of information subtitle to his book. When he lists discussion in that same section. (It is presented and the skill with which it these 15 causes in the first chapter, interesting to note, however, that has been organized. It is a worth- he mentions that this number is when Nassau explains charge- while investment for the serious somewhat arbitrary and that fewer, transfer colors in part 4, he attributes student of this complex but fascinat- more general, groupings would prob- the color of tanzanite to an iron- ing subject. titanium combination like the one in BOB EFFLER ably be sufficient to cover the physi- Course Development, GIA cal origins of color. No matter how blue sapphire. Other researchers the topics are divided, however, this have identified vanadium as the reviewer has seen no other book with coloring agent of tanzanite.] In the CASTELLANI AND as comprehensive a survey of the section on band theory and color col- GIULIANO: REVIVALIST basic processes behind color as this lectors, Nassau discusses color in di- amonds and metals, and devotes JEWELLERS OF THE one. It fills a long-standing gap in the 19TH CENTURY scientific literature. Dr. Nassau has some attention to the influence of radiation and heat on certain gem By Geoffrey C, Munn, foreword by effectivelv collected in one volume a "A. I<. Snowman, 208 pp., illus., publ. mass of information that was previ- colors. Part 6 deals with the scatter- by Rizzoli International Publica- ously scattered in a broad assortment ing phenomena seen in asteriated tions, New York, 1984 (French lan- of books an,d journal articles, some of and cat's-eye stones, as well as with guage edition pnbl. by Office du which he had authored. the interference and diffraction ef- fects seen in feldspars and opal. Livre, Fribourg, Switzerland, 1983). Following the introduction US$60.00* (which provides definitions of color, The last section of the main text, the spectrum, chromaticity, co- titled "Color-Related Topics," cov- Rarely has so authoritative and well lor-mixing schemes, color percep- ers such fascinating subjects as vi- written a monograph been published tion, models of light behavior, and sion, paint deterioration, color in the field of jewelry arts, or has so energy considerations], the next five changes in food, lasers, and hologra- handsome a tribute been paid to its sections examine the 15 causes of phy. It also provides a summary of subjects. This is the first definitive color. Each section deals with a broad gemstone coloration. These discus- study of the two Italian artist- group of color origins and relates sions help tie together the ideas pre- jewelers whose work represents the them to a particular model or physi- sented in the preceding sections and essence of 19th-century eclecticism cal theory. Almost all involve, in one also flesh out the general concepts and who founded the movement way or another, the interaction of with additional examples. However, called "Archaeological jewelry," in- light and electrons. in the summary on gem colors, Nas- spired by discoveries in Greece, Italy, Various gemstones are cited as sau neglects to specify whether or Russia, and Egypt. examples in all but one of these five not the yellow and green sapphires Fortunato Pio Castellani sections. Although most of these ex- colored by nickel are synthetics; the (1793- 1865) opened a shop in Rome amples have appeared in articles colors of the natural varieties are at- in 1814, and began making repro- published previously by Dr. Nassau, tributed to iron. At the end of each ductions of Greek and Etruscan jew- he does include an interesting- inter- chapter there are problems and elry with a quality of granular and pretation of the padparadscha color questions for the reader who enjoys a filigree work unknown since antiq- in the section involving ligand field challenge. With this feature, the uity. The accuracy of these repro- effects. Ruby, emerald, and alex- book could readily be used as the text ductions, achieved by craftsmen anclrite form a significant part of the for a college-level course. Castellani discovered who were still Although the author has placed using ancient techniques, gained some of the difficult and more tech- him an international reputation. nical details in the appendices, the After his death, the work was carried main body of the text remains a fairly *This book is available for purchase atp on by a son, Augusto (1829-1914], the GLA Bookstore, 1660 Stewart Street, advanced treatment. One of the ap- whose style and technique were so Santa Monica, CA 90404. pendices is an extensive reading list similar to his father's that, with few Book Reviews GEMS & GEMOLOGY Summer 1984 123 exceptions, his pieces are difficult to sources of design inspiration and the lished by Mr. Muinme himself, and it date. Augusta Castellani later became development of technical virtuosity. obviously involves his own lengthy director of the Capitoline Museum He has so successfully presented studies of the various emerald- in Rome, and much of his collection their full characters as goldsmiths, producing areas of the world, Unfor- remains there today. An elder antiquarians, art dealers, and liberal tunately, while the book contains brother, Alessandro [1824-1883),was political thinkers that we have not much interesting and valuable in- also a collector and dealer in antique only the men and their manners- formation, the facts are uneven and jewelry, and did much to promote their art expressed in the 200 sump- the absolutely unbelievable proof- the firm at the major exhibitions of tuous, and for the most part previ- reading leaves one aghast. The book art and industry held in Europe and ously unpublished, photographs- begins with, "Emerald is a gem- America after 1851. Much of the an- but also their private thoughts, their quality member of the Beryl family. tique jewelry in the British Museum attitudes toward patrons and clients, It is one of the gem Kingdom's truly was acquired through Alessandro, and their methods of salesmanship. precious stones, the others being di- and many of the pieces served as The technical chanters of the amond and mbv." In these fascinat- models for the firm's production. book are as compelling as the art- ing sentences, beryl and kingdom are The London and Paris branches, historical ones, with classical metal- capitalized, but no other words. One opened in the 1860s, gained an inde- lurgy, enamel, mosaics, and electro- also does not expect to see words pendent reputation under manager types receiving literate and percep- such as "distained," "stupidy," or Carlo Giuliano [c. 1831- 1895) and tive consideration. The important "posponed" throughout a profes- his son, Arthur (c. 1864- 1914).Carlo matter of marks (genuine and spuri- sional publication. Every editor (or Giuliano's work differs from other ous) is given attention, and the au- author) misses a couple in the course jewelry in its refinement and supe- thor has been meticulous in his ore- of a book or article, but not in virtu- rior execution. Although Giuliano sentation of extensive notes, a glos- ally every chapter and on almost also worked in the Greek and Etrus- sary, and a comprehensive bibliogra- every page. can styles, he developed a manner phy listing both exhibitions and sales One can get carried away with distinct from Castellani, and created where Castellani and Giuliano what are really rather minor criti- jewelry unlike any other made pieces figured prominently. cisms, in a sense, but errors such as before. His knowledge of antique and This book has clearly been a those cited above are annoying and Renaissance jewels is obvious, but labor of love 011 Mr. Munn's part, and distracting. The many good summa- his own pieces are not simply essays his publishers have supported him ries in this book, and its usefulness as in archaeological reconstruction. wholeheartedly by turning out what a compilation of information from While the Castellanis applied their must be regarded as the major con- all over the world are weakened bv superb craftsmanship and unerring tribution to jewelry history to appear sentences like the one that appears taste to reproductions expressing the so far in this decade. on page 62: "According to Julius style of their time and the values of NEIL LETSON Fetch, Jr., the Ida Oberstein expert, archaeological scholarship, Giul- Anniston, Alabama the source could be nearly as impor- iano's pieces are more imaginative THE EMERALD tant a supply as Brazil." The name is and no less finely made. His attitude Petsch, the city is Idar-Oberstein, By I. A. Mumme, 135 pp., illus., pub]. toward the past was that of an artist and the result is irritating. by Mumme Publishing, Australia, rather than a scholar. His later At the end of the book, Mumme 1982. US$21.00* works, made in the light, elegant discusses the separation of natural forms of the turn of the century, are The title page of this book reads, from synthetic emerald, and presents distinctive and express understand- "The Emerald: Its Occurrence, Dis- some material which suggests that ingand sympathy with the jewelry of crimination, and Valuation, by I. A. he has never done it himself and that Egypt, of the 16th century, the Ori- Mumme B.Sc. Hons. (Mineralogy he does not really understand gem ent, and Art Nouveau, but do not re- and Petrology), M.Eng.Sc., A.M. identification. For example, his ref- flect transiently fashionable tastes; Aust. Imm., etc. Formerly Chairman erence to a test for opacity, using a it is the stature of his own personal- of the Federal Board of Studies in Ed- photographic method, is backwards. ity as an artist-jeweler that is most ucation of the Gemmological Asso- One wonders, when much of this apparent. ciation of Australia and Convener for material is available elsewhere, just Geoffrey Munn (himself a jew- Education of the Geological Society what the purpose of this book is, and eler and a director of the London firm of Australia (New South Wales whether it should not have been of Wartski, Ltd.) has skillfully drawn Branch). Member of the Scientific submitted to a number of outsiders a vivid and fascinating portrait of the Education Panel of the Lapidary Club for conlnlent, criticism, and proof- personalities and firms of Castellani of New South Wales." At the bottom reading before it was put into such and Giuliano, placing each in its cor- of the page, it reads: llMumme Publi- flawed print. rect historical setting, tracing the cations." The book is evidently pub- RICHARD T. LIDDICOAT, JR. 124 Book Reviews GEMS & GEMOLOGY Summer 1984