CHAPTER 6 Physical Properties of Minerals
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Phenomenal Gemstones Possess Striking Optical Effects, Making Them Truly a Sight for Sore Eyes
THE PHENOMENAL PROPERTIES OF GEMS Phenomenal gemstones possess striking optical effects, making them truly a sight for sore eyes. Here is GIA’s guide to understanding what makes each phenomenon so uniquely brilliant. ASTERISM CROSSING BANDS OF REFLECTED LIGHT CREATE A SIX-RAYED STAR-LIKE APPEARANCE. ASTERISM OCCURS IN THE DOME OF A CABOCHON, AND CAN BE SEEN IN GEMS LIKE RUBIES AND SAPPHIRES. ADULARESCENCE THE SAME SCATTERING OF LIGHT THAT MAKES THE SKY BLUE CREATES A MILKY, BLUISH-WHITE GLOW, LIKE MOONLIGHT SHINING THROUGH A VEIL OF CLOUDS. MOONSTONE IS THE ONLY GEM THAT DISPLAYS IT. AVENTURESCENCE FOUND IN NATURAL GEMS LIKE SUNSTONE FELDSPAR AND AVENTURINE QUARTZ, IT DISPLAYS A GLITTERY EFFECT CAUSED BY LIGHT REFLECTING FROM SMALL, FLAT INCLUSIONS. CHATOYANCY OTHERWISE KNOWN AS THE “CAT’S EYE” EFFECT, BANDS OF LIGHT ARE CAUSED BY THE REFLECTION OF LIGHT FROM MANY PARALLEL, NEEDLE-LIKE INCLUSIONS INSIDE A CABOCHON. NOTABLE GEMS THAT DISPLAY CHATOYANCY INCLUDE CAT’S EYE TOURMALINE AND CAT’S EYE CHRYSOBERYL. IRIDESCENCE ALSO SEEN IN SOAP BUBBLES AND OIL SLICKS, IT’S A RAINBOW EFFECT THAT IS CREATED WHEN LIGHT IS BROKEN UP INTO DIFFERENT COLORS. LOOK FOR IT IN FIRE AGATE AND OPAL AMMONITE (KNOWN BY THE TRADE AS AMMOLITE). LABR ADORESCENCE A BROAD FLASH OF COLOR THAT APPEARS IN LABRADORITE FELDSPAR, IT’S CAUSED BY LIGHT INTERACTING WITH THIN LAYERS IN THE STONE, AND DISAPPEARS WHEN THE GEM IS MOVED. INSIDER’S TIP: THE MOST COMMON PHENOMENAL COLOR IN LABRADORITE IS BLUE. PLAY OF COLOR THE FLASHING RAINBOW-LIKE COLORS IN OPAL THAT FLASH AT YOU AS YOU TURN THE STONE OR MOVE AROUND IT. -
Star Stones (Asterism)
Learning Series: Basic Rockhound Knowledge Star Stones (Asterism) When parallel, needle-like inclusions, or tube-like channels, are oriented along two or more of the crystal faces of a mineral, and when that stone is cut as a domed cabochon, a four- to six-rayed figure is displayed on the dome. This phenomenon of reflected light is called "asterism" and the gems are called star stones. The most commonly seen examples are star corundums; where there are inclusions of titanium oxide (rutile or "silk") parallel to three crystal faces giving a six-rayed star. In rare cases, a twinned crystal slightly offset with its own set of rutile needles can lead to the formation of a twelve-rayed star. Although rutile is an extremely common inclusion in sapphire, few good, natural, star sapphires are found. One of the major reasons is that the heating, which is almost universally done to sapphire rough, dissolves rutile needles; clarifying and sometimes color enhancing the stone, yes, but eliminating potential stars! [Rutile needles (silk) aligned in three directions in unheated corundum] [Star ruby, white star sapphire ring, rare bi-colored star sapphire] The only other gem which commonly forms stars is quartz, where the phenomenon tends to be more visible in transmitted than in reflected light. In this species, rose quartz is the most frequently asterated variety. Most citrine in commerce has been heated, which tends to dissolve the fine rutile inclusions necessary for star formation, so it is rather rare. In fine, near-transparent quartzes which have been cut to a spherical shape, multiple stars can form an intersecting pattern over the surface. -
Mining, Geology, and Geological History of Garnet at the Barton Garnet Mine, Gore Mountain, New York William Kelly
6: RARE EARTH ELEMENT AND YTTRIUM MINERAL OCCURENCES IN THE ADIRONDACK MOUNTAINS 7 MINING, GEOLOGY, AND GEOLOGICAL HISTORY OF GARNET AT THE BARTON GARNET MINE, GORE MOUNTAIN, NEW YORK WILLIAM KELLY New York State Geologist, Emeritus, Division of Research and Collections, New York State Museum, Albany, NY 12230, [email protected] KEYWORDS: Garnet, Mining, Gore Mountain, Metamorphism, Lyon Mountain Granite ABSTRACT Garnet megacrysts commonly 30 centimters (cm) ranging up to 1 meter (m) in diameter occur at the summit of Gore Mountain, Adirondacks, NY and were mined there for abrasives for more than a century. The mine, owned by Barton Mines Co., LLC, is roughly 2 km x 150 m and is located in a hornblende-rich garnet amphibolite at the southern boundary of a metamorphosed olivine gabbro body that is in fault contact with charnockite. Barton supplies garnet, a chemically homogeneous pyrope-almandine, to the waterjet cutting, lapping, and abrasive coatings industries. The garnet megacrysts are reliably dated at 1049 ± 5 Ma. The growth of the garnet megacrysts was facilitated by an influx of hydrothermal fluid emanating from the ore body’s southern boundary fault. The fluids were most probably associated with the intrusion of the Lyon Mountain Granite (1049.9 ± 10 Ma) and/or associated pegmatitic rocks late in the tectonic history of the Adirondacks. INTRODUCTION The Adirondack Mountains in upstate New York are a small outlier of a larger body of rocks of similar age and geologic history that is located to the north in Canada. The Adirondack region can be loosely divided into amphibolite metamorphic facies Lowlands, in the northwest, and the granulite facies Central Highlands, which are 86 THE ADIRONDACK JOURNAL OF ENVIRONMENTAL STUDIES VOLUME 21 87 7: MINING, GEOLOGY, AND GEOLOGICAL HISTORY OF GARNET AT THE BARTON GARNET MINE, GORE MOUNTAIN, NEW YORK separated by a very large, northwest-dipping fault zone. -
UNITED J STATES PATENT OFFICE
Patented Nov. 15, 1949 ’ 2,488,507 UNITED j STATES PATENT OFFICE , SYNTHETIC STAR RUBIES AND STAR SAP PHIRES, AND PROCESS FOR‘ PRODUCING SAME John N. Burdick and John w. Glenn, Jr., Ken more, N. Y., assignors to The Linde Air Prod ucts Company, a corporation of Ohio No Drawing. Application August 27, 1947, Serial No. 770,942 19 Claims. (01. 63-82) 1 This invention relates to a process for develop Other-objects are to provide a process for ing asterism in natural and synthetic corundum developing asterism in single crystals of ruby. crystals, such as crystals of ruby and sapphire, and sapphire containing oxide of titanium; to which contain oxide of titanium dissolved in provide a process for obtaining star ruby and alumina. The invention is also concerned with .star sapphire gemstones from non-asteriated asteriated single crystals of synthetic corundum single crystals of ruby and sapphire containing as articles of manufacture, for example synthetic oxide of titanium; and to provide a process for star rubies and star sapphires. intensifying asterism inasteriated ruby and sap For more than thirty years massive nongran phire crystals. ular synthetic rubies and sapphires of gem qual 10 The term “massive non-granular,” as used ity have been produced commercially on a large herein, is intended to designate singlev crystals scale by the process of Verneuil, as disclosed in as distinguished from‘ a sintered or agglomerated U. S. Patents 988,230 and 1,004,505. In that proc mass of granules. Moreover, this term is further } ess powdered alumina, with or without small intended to designate crystals which are larger percentages of coloring oxides, drops through 15 than such tiny particles or granules of corundum an oxy-h'ydrogen ?ame, fuses, and accumulates as are commonly employed in abrasives, those on a refractory support until a long, narrow, crystals designated by the term “massive non approximately cylindrical boule of the desired granular” being, indeed, large enough to be used size is formed. -
Definition of a Mineral Each Mineral Species Has Unique and Identifiable Physical Properties. Form and Habit Terms (Crystal Grow
Definition of a Mineral • A mineral is a naturally occurring, • homogeneous solid with a Physical Properties of Minerals • definite, but not fixed, composition, and Color, shape, density, • an ordered atomic arrangement that is hardness, etc • formed by inorganic processes. • A mineral is a natural, crystalline phase. Form and Habit Terms Each mineral species has (Crystal Growth Forms) unique and identifiable • Prismatic (well developed prism physical properties. faces) (Pyramidal) • Form and habit (Shape) • Columnar (Irregular prism faces) • Luster • Acicular (needle-like) • Color and Streak • Botryoidal (rounded growth surface) • Cleavage and Fracture • Tabular (Platey) • Hardness • Stellate (Radiating) • Density • Fibrous (fibers, asbestiform) • Tenacity • Dendritic (tree-like) Acicular Fibrous 1 Dendritic Dendritic Radiating Radiating Bladed Botryoidal 2 Prismatic Luster and Transparency • Luster • Transparency – Metallic – Opaque – Resinous – Translucent (waxy) – Transparent – Pearly – Greasy – Adamantine – Vitreous Metallic Adamantine Color and Streak • The reflectance color of minerals is strongly affected by transition metals (V, Cr, Mn, Fe, Co, Ni, and Cu). (Also rare earths) Vitreous Pearly • Color in hand specimen may not be diagnostic. • Color in streak generally indicates presence of iron or other transition metals. Chatoyance, Asterism, Asterism: Star Sapphire and Luminescence • Chatoyance and asterism are optical effects due to diffraction of light from small inclusions. • Luminescence is emission of light. – Visible or UV (black light) – Tribo-luminescence: glow when rubbed – Cathodo-luminescence is emission of light from electron bombardment 3 Cleavage and Fracture Hardness What scratches what? • Crystals tend to break on planes of • 1. Talc 6. Orthoclase weakness. • 2. Gypsum 7. Quartz – Cleavage: perfect – Parting: irregular • 3. Calcite 8. Topaz – Hackly: very irregular • 4. Fluorite 9. -
Volume 35 / No. 1 / 2016
GemmologyThe Journal of Volume 35 / No. 1 / 2016 The Gemmological Association of Great Britain Save the date Gem-A Conference Saturday 5 and Sunday 6 November 2016 Visit www.gem-a.com for the latest information Join us. The Gemmological Association of Great Britain, 21 Ely Place, London, EC1N 6TD, UK. T: +44 (0)20 7404 3334 F: +44 (0)20 7404 8843. Registered charity no. 1109555. A company limited by guarantee and registered in England No. 1945780. Registered Office: 3rd Floor, 1-4 Argyll Street, London W1F 7LD. Conference_03-2016_March-April_Save The Date_A4.indd 1 12/04/2016 10:44:17 Contents GemmologyThe Journal of Volume 35 / No. 1 / 2016 COLUMNS p. 22 1 What’s New DiamondDect for diamond identification|Triple D photo kit|Upgraded Diamond- View|Variofoc LED lighting system|AGTA Tucson seminars| Responsible sourcing of coloured stones report|World Gold Council report|GSJ 2015 Annual Meeting abstracts|ICGL Newsletter|Large CVD synthetic diamond seen p. 64 by HRD Antwerp|MAGI diamond type report|SSEF Facette|Updated Journal cumulative index|Wyoming jade report|GemeSquare app and GemePrice 5.0|Historical reading lists|Hyperion inclusion search engine|Gems from the French Crown Jewels exhibit ARTICLES 6 Gem Notes Apatite from Iran|Purple apa- Feature Articles tite from Namibia|Cordierite from Madagascar|Emerald 28 Characterization of Oriented Inclusions in Cat’s-eye, and pyrite mixture from Co- Star and Other Chrysoberyls lombia|Garnet from Mahenge, By Karl Schmetzer, Heinz-Jürgen Bernhardt and H. Albert Gilg Tanzania|Grandidierite from -
Jog 35 5.Pdf
GemmologyThe Journal of Volume 35 / No. 5 / 2017 The Gemmological Association of Great Britain Contents GemmologyThe Journal of Volume 35 / No. 5 / 2017 COLUMNS p.386 373 What’s New Multi-colour-temperature lamp|PL-Inspector|AGTA report on Myanmar|ASEAN Gem & p. 388 Jewelry Review|Atypical pearl culturing in P. maxima|Conflict diamonds and Cameroon| Diamond origin identification using fluorescence|Global Diamond Industry 2016|ICGL Klaus Schollenbruch photo Newsletter|Japanese journal online|Raman spectrometer sensitivity|Gold demand trends 2016|Agate Expo DVDs|AGTA ARTICLES 2017 Tucson seminars|Color- Jeff Scovil photo Codex colour referencing system| Feature Articles GemeSquare and MyGem- ewizard apps|Gemewizard 404 Synthetic Emeralds Grown by W. Zerfass: Historical monitor calibration kit|Fabergé Account, Growth Technology, and Properties online|Reopening of The Lap- By Karl Schmetzer, H. Albert Gilg and Elisabeth Vaupel worth Museum of Geology 378 Practical Gemmology 416 Rethinking Lab Reports for the Geographical Moonstone mystery Origin of Gems By Jack M. Ogden 380 Gem Notes Red beryl matrix cabochons| Gemmological Briefs Ceruleite from Chile|Yellow danburite from Namalulu, 424 Fake Pearls Made from Tridacna gigas Shells Tanzania|Emerald from By Michael S. Krzemnicki and Laurent E. Cartier Ethiopia|Vivid purplish pink fluorite from Illinois, USA| 430 Large 12-Rayed Black Star Sapphire from Sri Lanka Colourless forsterite from with Asterism Caused by Ilmenite Inclusions Vietnam|Sapphire from By Thanh Nhan Bui, Pascal Entremont and Jean-Pierre Gauthier Ambatondrazaka, Madagascar| Colour-change scorodite from 436 Tsumeb, Namibia|Stichtite| Excursions Zoned type IaB/IIa diamond| Mogok, Myanmar: November 2016 Synthetic star ruby 444 Conferences AGA Tucson|GIT|Jewelry Industry Summit Cover Photo: High-quality rubies, sapphires 450 Letters and emeralds are typically ac- companied by geographical origin reports from gemmologi- 451 Gem-A Notices cal laboratories, as discussed on pp. -
Rendering Precious Gems
RENDERING PRECIOUS AND SEMI-PRECIOUS GEMS PERSONAL REASONING Part of the research for my thesis – Glyptics Portrait Generator Glyptics is the art of producing engraved gems This seminar is the research of gemstone properties Roman Emperor Caracalla engraved in amethyst WHAT IS A GEM? A precious stone of any kind, esp. when cut and polished for ornament; a jewel. CLASSIFICATION Gemstones Precious Semi-precious CLASSIFICATION Precious only 4 gems Can you name them? CLASSIFICATION Precious only 4 gems • Emerald • Ruby • Sapphire • Diamond CLASSIFICATION • Agate Semi-precious • Alexandrite too many to list all of them here • Amethyst • Ametrine • Apatite • Aquamarine • Aventurine • Azurite… And those are not even all the gems, starting with an “A” GENERAL PROPERTIES GENERAL PROPERTIES • Refraction and sometimes birefringence • Produces dichroism (multi-coloring) and doubling GENERAL PROPERTIES • Refraction and sometimes birefringence • Internal reflections • Produce brilliance – light, reflected from the inside GENERAL PROPERTIES • Refraction and sometimes birefringence • Internal reflections • Dispersion • Produces fire – splitting light into colors of the spectrum GEMSTONE CUTTING Improper cutting affects internal reflectiveness => brilliance REFRACTIVE INDEX • Different gems have different refractive indices • In case of birefringence, gems have two refractive indices • Higher RI means higher brilliance • Diamond has a RI of 2.42, while ruby has 1.76 Refractometer – device for measuring refractive index SO… HOW TO RENDER THAT? SO… HOW TO -
C:\Documents and Settings\Alan Smithee\My Documents\MOTM
Cdbdladq1//5Lhmdq`knesgdLnmsg9Qtax “Few gems have the mysterious depth of color, the glittering history, and the aristocratic dignity of the corundum gems.”--Walter Schumann, Gemstones of the World OGXRHB@K OQNODQSHDR Chemistry: Al2O3 Aluminum Oxide; ruby variety always contains traces of chromium and sometime iron and titanium Class: Oxides Subclass: Simple Oxides Group: Corundum-Hematite Crystal System: Hexagonal Crystal Habits: Usually as tapering, prismatic or pyramidal crystals in rough and rounded barrel shapes, often striated. Ruby variety often tabular. Also as granular masses. Color: Corundum occurs in many colors, including blue, red, pink, yellow, brown, and gray; Ruby refers specifically to red or pinkish-red corundum, sometimes with hints of brown, orange, blue, or purple; all other colors are called sapphire. Color zoning common. Luster: Adamantine to vitreous Transparency: Transparent to translucent Streak: White Cleavage: None, sometimes exhibits three-directional parting. Figure 1 Simple ruby Fracture: Conchoidal to uneven; brittle. crystal showing Hardness: 9.0 hexagonal form. Specific Gravity: 3.9-4.1 Luminescence: Fluorescent Refractive Index: 1.757-1.778 Distinctive Features and Tests: Red color (in ruby corundum), extreme hardness, moderately high density, and striations on parting faces. Dana Classification Number: 4.3.1.1 M @L D The name of this month’s mineral, which is correctly pronounced coh-RUN-dum, is derived from the ancient Sanskrit word for ruby, kuruvinda. The variety name “ruby” stems from the Latin -
300 on the CAUSE of ASTERISM in STAR CORUNDUM K. Nesseu
300 MINERALOGICAL NOTES KnNNrov, G. C. (1950) Pressure-volume-temperature relations in water at elevated temperatures and pressures. Amer. f . Sci,.2481 540-564. Klnern, W. (1940) Kristallographische Untersuchungen am Aragonit unter besonderer Berucksichtigung des Vorkommens am Erzburg, Steirmark. N euesJakrb. Minad, Abt. ,4, Beil.-Bd. 75,465. M,LcDoNar.o, G. J. F. (1956) Experimental determination of calcite-aragonite equilibrium relations at elevated temperatures and pressures: Amer. Mineratr.4lr lM-756. Wnev, J. L., euo DeNrnr.s, F. (1957) Precipitation of calcite and aragonite: f . Amer. Chem. 50c.79,2031. THE AMERICAN MINERAI,OGIST, VOL. 53, JANUARY_FEBRUARY, 1968 ON THE CAUSEOF ASTERISMIN STAR CORUNDUM K. Nesseu, Bell TelephoneLaboratories, Inc. Murray HilI, Neu Jersey. INtnooucuoN It has beengenerally accepted that asterismin corundum (star rubies and sapphires)is causedby needlesor rutile (TiOz) aligned along crystal- lographic planes of the corundum (e.g. Webster, 1962). The evidence given ty Tait (1955) was: (1) the presenceof titanium, (2) the needle- like habit, and (3) the squarecross-section of the needles.Based on the analogy with rutilated quartz, and by eliminating octahedrite and brook- ite by the morphology, rutile was accordingly identified. This type of evidence,however, is explained equally well by either TiOr or the com- pound aluminum titanate Al2TiO6. ConuNrulr Gnowrn CousrrBnetroNs The technique for the laboratory growth of star rubies and sapphire has beenrevealed in patents by the Linde Division of the Union Carbide Corp. (Burdick et aI., 1949, 1954). Corundum is grown by the Verneuil technique with the addition of, preferably, 0.1 to 0.3 percent titanium oxide in the feed powder. -
Ruby – the July Birthstone
Learning Series: Birthstones – July Ruby – The July Birthstone Background The story of the July birthstone traces to the ancient Silk Road of China. Notes about the transport of rubies can be found all the way back to 200 BC, as Asian traders imported rubies into to their native cultures where they were held in very high regard for their gem quality and red color; a good luck color in many Asian cultures. Rubies were used not just for jewelry, but to ornament armor, scabbards and harnesses for wealthy noblemen. Some wealthy people even laid rubies into the foundations of their homes as a good luck charm. The word “ruby” comes from the Latin "ruber," meaning red. It is a variety of the mineral Corundum and for a ruby to be born in the natural environment, a perfect combination of aluminum oxide, correct temperature, correct pressure in the earth’s crust and very low silicon content is a requisite. This makes rubies very rare and large rubies (over 2 carats) even rarer. Host rocks of rubies often include metamorphic dolomite marbles, gneiss, and amphibolite. However, rubies are not normally extracted from the primary deposits due to the high cost of mining. They are retrieved from the secondary deposits which are usually alluvial. Mining of rubies is still fairly primitive and takes many man-hours of labor to find the stones. Once the gem bearing alluvial material is identified, then the gravel is sifted through wire screens and picked out by hand. Rubies were once known in eastern legends as “blood drops from the heart of the Mother Earth”. -
(130) Twins and Rutile Precipitates in Chrysoberyl Crystals from Rio Das
REVISION 1 1 Structural investigation of (130) twins and rutile precipitates 2 in chrysoberyl crystals from Rio das Pratinhas in Bahia (Brazil) 3 4 Sandra Drev,1 Matej Komelj,1 Matjaž Mazaj,2 Nina Daneu1 and Aleksander Rečnik1 5 6 1 Department for Nanostructured Materials, Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia 7 2 Laboratory for Inorganic Chemistry, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia 8 9 10 11 Abstract. We studied V-shaped twins of chrysoberyl (BeAl2O4) from Rio das Pratinhas 12 pegmatites near Arataca in the Bahia state of Brazil. The local structure of the twin boundaries 13 was determined using powder X-ray diffraction analysis (XRD), transmission electron micros- 14 copy (TEM) methods and density functional theory (DFT) calculations. To provide the most re- 15 liable model for DFT and HRTEM simulations the structure of chrysoberyl was first refined in 16 the orthorhombic space group 62 (Pmnb) with unit cell parameters: a = 5.4825(1) Å, b = 17 9.4163(2) Å and c = 4.4308(1) Å, with 0.5 at% of Fe3+ present on the Al(2) sites, suggesting an 18 average composition of BeAl1.99Fe0.01O4. TEM study of V-shaped twins showed that the twin 19 boundary lies in the (130) planes, and the angle measured between the crystal domains relat- 20 ed by mirror twin operation is ∼ 59.5°. Rigid structural model of (130) twin boundary in 21 chrysoberyl was refined by DFT calculations, using a pseudo-potential method. The twin 22 boundaries show local enrichment with Ti.