CONNOISSEUR'S CHOICE

CALVIN J. ANDERSON JOHN RAKOVAN Calvin Anderson is a graduate student working on the struc- Department of Geology and ture, chemistry, and texture of wire for a master’s of sci- Environmental Earth Science ence degree at Miami University in Oxford, Ohio. 250 South Patterson Avenue Dr. John Rakovan, an executive editor of Rocks & Miner- Miami University als, is a professor of mineralogy and geochemistry at Miami Oxford, Ohio 45056 University in Oxford, Ohio. [email protected] [email protected] Wire Silver Kongsberg, Norway Wire Ground Hog& Mine, Gilman, Colorado

ince the dawn of civilization, silver and gold have been hand-stamped staters from Anatolia (western Turkey, about treasured for their surpassing beauty and captivating 600 BC) made of electrum, a natural of silver and gold luster. Some of the earliest known gold jewelry, dating (Wallace 1987). Throughout history and around the globe, Sfrom approximately 4500 BC, was found in a cemetery in gold and silver have been mined, refined, and fashioned into Varna, Bulgaria, on the west coast of the Black Sea (Gim- nearly every kind of object imaginable. But perhaps some butas 1977). Precious metals have been used for currency of the most intriguing examples of these beloved metals are around the Mediterranean since at least the third millen- those whose stunning and graceful forms cannot be attrib- nium BC (Balmuth 1975), and the oldest preserved coins are uted to the hand of man.

Figure 1. Section cut through a wire silver from Kazakhstan Figure 2. SEM image of a synthetic wire silver shows striations shows roughly equigranular texture as opposed to a bundle of superimposed on a roughly equigranular texture. From Anderson whiskers or a single crystal. From Anderson et al. (2017). et al. (2017).

Volume 92, July/August 2017 345 Figure 3. Wire silver, 21.6 cm tall, from Kongsberg, Norway. Cranbrook Institute of Science specimen, Jeff Scovil photo.

346 ROCKS & MINERALS Figure 4. Wire gold, 11.7 cm tall, from the Ground Hog mine, Gillman district, Eagle County, Colorado. Harvard Mineralogical and Geological Museum specimen, Jeff Scovil photo.

Volume 92, July/August 2017 347 The wire form is an unusual and relatively rare mineral generally too expensive for use in wiring, and its propensity habit characterized by elongate hairlike growths with lon- for oxidizing (tarnishing) prevents it from being employed gitudinally parallel striations and wiry, twisting, sometimes in electrical contacts, as gold is often used. One historic ap- contorted, tendrils. Anderson et al. (2017, p. 11) published plication of silver has been in photography in the form of the first study on the crystallinity and texture of wire silver. silver halide film. Native silver crystallizes as isometric They found that although silver wires might appear to be (hexoctahedral class) crystals and can be found in a variety single crystals or polycrystalline bundles of whisker-shaped of habits including massive, reticulated, dendritic, arbores- crystals, they are actually polycrystalline with striations cent, and, of course, wire habits (e.g., Wallace, Barton, and “merely superimposed on an equigranular grain texture” Wilson 1994; Cook 2003). (figs. 1 and 2). Very few minerals assume the wire habit, the Our Connoisseur’s Choice for wire silver, standing 21.6 most prominent of which are the illustrious silver and gold. cm tall, is an impressive specimen from the mineral col- In this Connoisseur’s Choice column we highlight examples lection of the Cranbrook Institute of Science in Bloomfield of both wire silver and wire gold. Hills, Michigan. It was purchased from Martin Ehrmann by the Cranbrook Institute of Science in 1963 with money Wire Silver from the Goddard Fund (see Zawiskie 2017). It is arguably Silver is a highly malleable and ductile metal with a bril- the best and certainly the largest example of Kongsberg wire liant white luster, a result of its excellent reflectance across silver in the United States (fig. 3). the entire visible spectrum. It has a hackly fracture and is Officially discovered in 1623, the mines of Kongsberg, relatively soft with a Mohs hardness of 2.5–3; a specific grav- Norway, were a historic source of silver specimens for more ity of 10.5 imparts a pleasing heft to it. Silver is diamagnetic than 330 years. Located some 80 kilometers west-southwest and has the highest electrical conductivity of any metal but is of the capital city of Oslo, Kongsberg hosts approximately three hundred mines that collectively produced an estimated 43 million troy ounces of silver before they closed in 1957. The veins are hosted in various Precambrian gneisses and amphibolites with abundant fahlbands (narrow zones rich in sulfide minerals) cut by Permian diabase dikes. It is signifi- cant that “silver only occurs where the [calcite-bearing] veins cut the fahlbands . . . the two most important examples [of which] are the Overberget and the Underberget fahlbands” (Johnsen 1986, p. 26). In these intersections, thick, hearty, and coarse trådsølv (literally “thread silver”) are common occurrences (fig. 5), along with crystalline silver, abundant calcite, and other gangue minerals including acanthite, graphite, pyrite, galena, and silver-antimony sulfosalts. Although the formation of wire silver remains poorly un- derstood despite centuries of synthesis experiments (Henckel and Stephani 1747; Haüy 1801; Liversidge 1877; Vogt 1899; Kohlschütter and Eydmann 1912), Jensen (1939) argues and demonstrates that the wire silver of Kongsberg likely formed by hydrothermal processes. His hypothesis is consistent with the generally accepted idea that the Kongsberg silver deposits are probably synchronous with the Permian Oslo Rift (Johnsen 1986) and that the silver likely migrated in hydrothermal fluids from nearby black shales (Brandes and Brandes 2015). At Kongsberg, wire silver is frequently found on various gangue minerals including pyrite, galena, and cal- cite (Neumann 1944). Although the Kongsberg mines may have been the most significant in terms of native silver production, the Freiberg mining district of Saxony, Germany, is far older and equally famous. Established around AD 1168, some four and a half centuries earlier than Kongsberg, German mines produced some of the world’s finest silver for more than eight hundred years. It was in fact German miners (of the Harz district), because of their already historic experience, who were first Figure 5. Wire silver with calcite, 7 cm tall, from Kongsberg, brought in by the king of Denmark-Norway to work the Norway. Dave Bunk Minerals specimen, Jeff Scovil photo. mines in Kongsberg (Johnsen 1986).

348 ROCKS & MINERALS The Freiberg mining district is a network of veins hosted in the crystalline basement rocks of the Erzgebirge (“Ore Mountains”), a complex of gneisses, schists, amphibolites, and igneous intrusions, much like that of Kongsberg. The native silver is most concentrated where silver veins cross- cut sulfide-rich veins (Massanek, Neumeier, and Sandmann 2015). Although wire silver (haarsilber in German) can be found throughout the Erzgebirge, including mines in Jo- hanngeorgenstadt, St. Joachimsthal, Annaberg, and Marien- berg, the most famous and characteristic wire silvers are as- sociated with Freiberg (fig. 6) and, to a lesser degree, Schnee- berg (Lieber and Leyerzapf 1986). The Himmelsfürst mine in the Freiberg district, for example, has produced many museum-quality specimens exceeding 10 cm in length. St. Andreasberg, a mine in the Harz Mountains that has yielded some very fine heavy silver wires, also deserves an honorable mention. Typical Freiberg silvers are more slender and wiry, and more often associated with acanthite, than those from Figure 7. Wire silver on acanthite, 7 cm tall, from the Imiter mine, Ouarzazate Province, Morocco. Oliver Konczer speci- Kongsberg. Other important minerals from this deposit in- men, Jeff Scovil photo. clude galena, sphalerite, silver sulfosalts, barite, pyrite, chal- copyrite, fluorite, siderite, quartz, and calcite, although the was “rediscovered” in the 1950s and since has become one of latter two are rarely found together (Massanek, Neumeier, the world’s foremost silver mines (Barral, Favreau, and Lheur and Sandmann 2015). As at Kongsberg, it is unclear how 2011) still producing beautiful specimens of wire silver and these wires form. There has been no shortage of German sci- acanthite (fig. 7). entists who have attempted to unveil the mechanism behind In China, the Hongda mine in the Shanxi Province has this phenomenon (Bischof 1843; Opificius 1888; Friedrich yielded some very nice silver wires in recent years (fig. 8), and Leroux 1906; Kohlschütter and Eydmann 1912; Blaha

1957; Vogt 1899), but a cohesive explanation remains lack- ing. Further research will be necessary to solve this centu- ries-long mystery. In addition to Kongsberg and Freiberg, other localities have produced excellent wire silvers. Mining in the Imiter district, located in the heart of Mo- rocco, can be traced as far back as the eighth century AD. Al- though it was largely abandoned by the fourteenth century, it

Figure 8. Wire silver with acanthite and quartz, 12.2 cm tall, Figure 6. Wire silver, 7.5 cm wide, from the Freiberg district, from the Hongda mine, Shanxi Province, China. Mike and Sally Saxony, Germany. Scott Rudolph specimen, Jeff Scovil photo. Bergman specimen, Jeff Scovil photo.

Volume 92, July/August 2017 349 Figure 9 (left). Wire silver, 13.5 cm across, from Shaft 46, Dzhezkazgan mine, Karagandy Province, Kazakhstan. Carnegie Museum of specimen, Debra Wilson photo.

Figure 11 (below). Wire silver on quartz, 5.8 cm tall, from the Bulldog mine, Creede district, Mineral County, Colorado. Mike and Sally Bergman specimen, Jeff Scovil photo. although they tend to be smaller and less spectacular than those from Kongsberg and Freiberg. Also, Tongchong, Yun- nan Province, and Lujiang, Anhui Province, are home to some stunning pieces. The Dzhezkazgan mine in Kazakhstan, about 30 kilome- ters northwest of Zhezkazgan in the Karagandy Province, has produced some amazing specimens, often in mesmer- izing tangled masses (fig. 9). This locality also contains fine examples of chalcocite and rare minerals including

bornite, betekhtinite, and likasite. The Silver Islet mine in Ontario, Canada, mined exten- sively from the 1870s to 1970s, produced some exceptional specimens, several of which are now on display in the Royal Ontario Museum (fig. 10). Silver Islet wire silvers tend to be fairly thick, somewhat resembling those of Kongsberg

(Wilson 1986). Also, the Highland Bell mine in Beaverdell, British Columbia, has yielded many wire silvers, often asso- ciated (and sometimes encrusted) with acanthite (Ingelson and Mussieux 1989). Museum-quality examples of wire silver from the United States are comparatively few. Although wires have been Figure 10. Wire silver with calcite, 11 cm tall, from the Silver found infrequently in many places, especially in the western Islet mine, Ontario, Canada. Royal Ontario Museum specimen, states, arguably the best specimens have come from the Bull- used with permission of the Royal Ontario Museum © ROM. dog mine, in Mineral County, Colorado (fig. 11).

350 ROCKS & MINERALS Figure 12 (left). Wire silver, 9.8 cm tall, from the Batopilas district, Chihuahua, Mexico. Former Miguel Romero specimen, Jeff Scovil photo.

Figure 13 (right). Wire silver on polybasite, 5 cm tall, from Guanajuato, Mexico. Albert and Sue Liebetrau specimen, Jeff Scovil photo.

Mexico’s most important source of wire silver is the Bato- pilas district in southwest Chihuahua (fig. 12). Between the mid-seventeenth and twentieth centuries, it is estimated to have produced as much as 300 million troy ounces of silver, approximately seven times that of the legendary Kongsberg (Wilson and Panczner 1986). Productive mines in Zacatecas and Guanajuato (fig. 13) have also generated many collect- ible wires, although they are generally smaller. Peruvian silvers, especially those from the Uchucchacua mine (fig. 14), have recently captured the attention of many collectors. This remote location is in the central Andes Mountains approximately 160 kilometers north-northwest of Lima. Cook (2003) has already highlighted some of the best wires from Uchucchacua and provided a good overview of other wire silver occurrences around the world.

Wire Gold Gold, like silver, is a familiar soft (Mohs 2.5–3), malleable, ductile metal with a characteristic bright yellow luster. Al- though similar to silver in many ways, gold is nearly twice as dense (specific gravity of 19.3) and up to eighteen times less abundant in Earth’s crust. Its radiant color and its resistance to corrosion or oxidation have made it the object of human desire since time immemorial. Thus, gold is currently, and historically, far more valuable per ounce than silver. It is the

Figure 14. Wire silver, 5.1 cm tall, from the Uchucchacua mine, Lima Department, Peru. Carnegie Museum of Natural History specimen, Debra Wilson photo.

Volume 92, July/August 2017 351 in both articles, both its locality and early provenance were COLOR SPONSORS for the Connoisseur’s Choice rediscovered. Argall opines that it “is beyond doubt, one of column during 2017 are the Houston Gem and Min- the finest gold specimens ever discovered.” eral Society, in memory of Arthur E. Smith, and the When economic ore deposits were discovered in the Gilman Cincinnati Mineral Society. district in about 1879, it became Colorado’s most impor- tant source of zinc as well as a rich producer of , cop- per, silver, and gold (Lovering, Tweto, and Lovering 1978). third most conductive metal behind silver and copper, highly “Between 1884 and 1925, rich gold ores were mined from resistant to corrosion, and chemically inert with respect to the oxidized, up-dip portion of several manto-replacement living tissue, making gold an excellent metal for jewelry. In deposits in the Sawatch Quartzite, with the highest grade minute quantities it is an excellent and dependable material ores in the district being found in the Ground Hog mine” for both high-efficiency electronics and sensitive medical (Warren and Pedersen 2003, p. 304). The chimney veins of applications. Again, like silver, gold crystallizes in the same the Ground Hog mine have produced amazing specimens isometric system (hexoctahedral class) and can be found in of wire gold. Large and robust with deep striations, they are many of the same morphologies, including wires. perhaps the best in the world. Virtually no data concerning the crystallinity of wire gold Gold wires from the Ground Hog mine are rivaled only has been published. Collectors are understandably averse to by those from Venezuela. Santa Elena de Uairen, in the Bo- subjecting their rare treasures to potentially damaging tests, livar Province, has produced some superb gold wires in re- and researchers have historically fixated on the formation of cent years. A marvelous specimen housed in the Treasures their magnitudes-more-abundant and less expensive cousin, wire silver, with few exceptions (Liversidge 1877; Beutell 1919). However, because of the unmistakable similarities between wire gold and silver, it is possible that many of the observations made of wire silver by Anderson et al. (2017) will be found to apply to wire gold as well. Nevertheless, wire gold also possesses some distinct dif- ferences when compared to wire silver. For instance, the striations, which are so striking in silver, are usually poorly

expressed in gold. This can be accounted for in a number of ways. First of all, the term gold wire has been used rather loosely among mineral collectors for any gold crystals re- sembling drawn-out and/or bent shapes. Upon close exami- nation, however, many of these specimens appear to be more dendritic or ribbonlike and, in some cases, elongate hop- pered octahedral or spinel-law twins. Perhaps these “pseu- dowires” are not true wires at all (Mauthner 2004). Another case might be those found as placer gold, whose striations may simply have been eroded away during transport. A third consideration was raised by Beutell (1919), who attempted to grow wire gold in the same way he had grown wire silver but was unsuccessful. In his experiments, gold wires formed only when the gold was argentiferous. It is true that many of the best-developed gold wires possess an electrum-esque color, and it is possible that these could contain an appre- ciable amount of silver. Because wires are rarely well-developed and a rare habit of gold, our Connoisseur’s Choice for wire gold, at 11.7 cm long, 1.9 cm thick, and weighing 8.5 ounces, may just be their king (fig. 4). This magnificent wire gold, named “the Gold Horn,” was collected in 1887 from the Ground Hog mine in Gilman, Colorado. However, the identity of the specimen’s locality had been lost until recently when, as Raines and Francis (2008, p. 223) describe, it was rediscovered: When acquired in 1948 as part of the Burrage collection, it was labeled “California,” as so many gold specimens are. For- tunately, the Ground Hog mine ore . . . was so unusual that it Figure 15. Wire gold, 12 cm tall, from the El Infierno mine, near was described in both the scientific (Argall 1893) and popu- Santa Elena de Uairen, Bolivar, Venezuela. MIM Museum speci- lar press (Anonymous 1893). Because the Horn is illustrated men, Augustin de Valence photo.

352 ROCKS & MINERALS Figure 18. Wire gold, 10.1 cm tall, from the Butte/Plumas county border, near Paradise, California. Mario Pauwels specimen, Jeff Scovil photo.

Figure 16. Wire gold, 3.6 cm wide, from Breckinridge, Colo- rado. Marty Zinn specimen, Jeff Scovil photo.

Room of the MIM Museum in Beirut, Lebanon, measures 12 cm tall, although the wire would undoubtedly measure longer if uncoiled (fig. 15). Little information is available concerning the geological setting of these deposits except for the general stratigraphy: Roraima Supergroup (Paleopro- terozoic sedimentary) and Precambrian basement complex cut by gabbroic intrusions and overlain by quaternary allu- samples are the San Juan Basin, Municipio de Novita, Chocó vial sediments (López, Mencher, and Brineman 1942; San- Department, Colombia, and the Julcani mine, Huancavelica tos et al. 2003). Some of the most productive sites are those Department, Peru. where the local rock has been weathered to soft clay. Two Unlike with wire silver, the United States has been the other important South American localities for fine wire gold source of many of the best examples of wire gold. The Wire Patch mine, Breckenridge, Colorado, just 30 kilometers east of Gilman, is famous for its “nests” of gold wires (fig. 16), although they often straddle the line between wires and either dendrites or perhaps highly elongate spinel-law twin crystals. One wire from Eldorado County, California, possesses strong striations and is 5.7 cm long (fig. 17). The Mad Mutha mine, Humboldt County, and the Olinghouse district, Washoe County, Nevada, along with the San Pedro mine, Santa Fe County, New Mexico, have produced wirelike specimens, but many of these are better described as pseu- dowires rather than as true gold wires. While Asia is not typically known for producing wire gold, the Cansuran mining district in the heart of the Su- rigao Peninsula, Mindanao, Philippines, may be an excep- tion. Although little information is available about the spe- cific location or geologic setting of these deposits, crystalline gold has been historically common there—and in several mines as wire gold (Eddingfield 1911). In addition, the Aro- roy mining district, Masbate, Philippines, is home to some beautiful wires (fig. 17). Many wires have been found as placer gold, perhaps the most impressive of which is “the Boomerang,” a 10.1-cm- long, 1.5-cm-thick wire found near Butte Creek, approxi- Figure 17. Wire gold, 7.6 cm tall, from the Aroroy mining mately 13 kilometers east of Butte Meadows, California (fig. district, Masbate, Philippines. Mike Bergman specimen, Jeff 18). Some smaller specimens have come out of the Little Scovil photo. Blanche Creek, Thistle Creek, and Freegold areas of the Yu-

Volume 92, July/August 2017 353 Cook, R. B. 2003. Connoisseur’s choice: Silver, Uchucchacua, Peru. Rocks & Minerals 78:40-45. Eddingfield, F. T. 1911. Cansuran mining district. In The mineral resources of the Philippine Islands for the year 1911, ed. W. D. Smith, 27–31. Manilla, Philippines: Bureau of Printing. Friedrich, K., and A. Leroux. 1906. Silber und Schwefelsilber. Met- allurgie 3:361–71. Gimbutas, M. 1977. Varna: A sensationally rich cemetery of the Karanovo civilization, about 4500 B.C. Expedition 1939:47. Haüy, R. 1801. Traitè de Minéralogie. Vol. 3. Paris, France: Delance. Henckel, J. F., and J. E. Stephani, eds. 1747. Henkelius in mineralogia redivivus. Dresden, Germany. Ingelson, A., and R. Mussieux. 1989. The Highland Bell mine, Bea- verdell, British Columbia. Mineralogical Record 20:441–46. Jensen, E. 1939. Sølvet på Kongsberg, om de kjemiske prosesser ved dets utfelling og om trådsølvdannelsen. Dissertation, University of Oslo, Department of Chemistry. JOFHoNr G eEm.s G& MAinReraSlsOW Johnsen, O. 1986. Famous mineral localities: The Kongsberg silver July 27-29 Franklin, NC 28734 mines, Norway. Mineralogical Record 17:19–36. Franklin Faceters’ Frolic Kohlschütter, V., and E. Eydmann. 1912. Über Bildungsformen The Factory, 1024 Georgia Rd. (US 441) des Silbers, Das Haarsilber. Justus Liebigs Annalen der Chemie August 3-6 Spruce Pine, NC 28777 390:340–64. NC Mineral and Gem Festival, 12121 S. 226 Hwy August 11-13 West Springfield, MA 01089 Lieber, W., and H. Leyerzapf. 1986. German silver: An historic East Coast Gem, Mineral & Fossil Show perspective on silver mining in Germany. Mineralogical Record Better Living Center, Eastern States Exposition, 1305 Memorial Ave. 17:3–18. August 18-20 Lebanon, PA 17042 Liversidge, A. 1877. On the formation of moss gold and silver. Gem Miners’ Jubilee, Mid-Atlantic Gem & Jewelry Association Lebanon Expo Center, 80 Rocherty Rd. Chemical News and Journal of Industrial Science 35:68–71. López, V. M., E. Mencher, and J. H. Brineman Jr. 1942. Geology Come see us at a gem & mineral show near you! of southeastern Venezuela. Geological Society of America Bulletin PO Box 594, Murrieta, CA 92564 53:849–72. Phone/Fax (951) 698-4833/Cell (818) 800-5644/[email protected] Lovering, T. S., O. Tweto, and T. G. Lovering. 1978. Ore deposits of www.johngarsow.com the Gilman district, Eagle County, Colorado. U.S. Geological Sur- vey professional paper 1017. Massanek, A., G. Neumeier, and D. Sandmann. 2015. The Frei-

berg mining district, Saxony, Germany. Mineralogical Record kon (Mauthner 2004) as well as various (and poorly docu- 46:311–72. mented) locations in Alaska. Mauthner, M. 2004. Morphology of gold crystals from the Yukon Territory, Canada. Rocks & Minerals 79:100–109. ACKNOWLEDGMENTS Neumann, H. 1944. Silver deposits at Kongsberg. Norges Geologiske We thank Dr. John Zawiskie for providing information about Undersøkelse 162. the history of our Connoisseur’s Choice wire silver. We are grateful Opificius, L. 1888. Darstellung von gediegenem Silber (Haarsil- to Bob Cook, Carl Francis, and John White for their reviews of the ber) auf künstlichem Wege. Chemiker-Zeitung 12:649. manuscript. Raines, E., and C. A. Francis. 2008. Colorado gold. American min- eral treasures, ed. G. A. Staebler and W. E. Wilson, 222-29. East REFERENCES Hampton, CT: Lithographie. Anderson, C. J., J. Rakovan, T. Böellinghaus, and V. Lüders. 2017. Santos, J. O. S., P. E. Potter, N. J. Reis, L. A. Hartmann, I. R. Fletcher, Crystallinity and texture of natural and synthetic wire silver. In and N. J. McNaughton. 2003. Age, source, and regional stratig- 44th Rochester Mineralogical Symposium program with abstracts, raphy of the Roraima Supergroup and Roraima-like outliers in ed. S. Chamberlain, 10–12. Rochester, NY: Rochester Academy northern South America based on U-Pb geochronology. Geologi- of Science. cal Society of America Bulletin 115:331–48. Anonymous. 1893. Gold in spirals. The Great Divide 9:46. Vogt, J. H. L. 1899. Über die Bildung des Silbers, besonders des Argall, P. 1893. Discussion of the paper of Mr. Rickard, “The ori- Kongsberger Silbers, durch Sekundärprocesse aus Silberglanz gin of the gold-bearing quartz of the Bendigo Reefs, Australia.” und anderen Silbererzen—Und ein Versuch zur Erklärung der American Institute of Mining Engineers Transactions 22:740–63. Edelheit der Kongsberger Gänge an den Fahlbandkreuzen. Balmuth, S. M. 1975. The critical moment: The transition from cur- Zeitschrift für praktische Geologie 7:113–23, 177–81. rency to coinage in the eastern Mediterranean. World Archaeol- Wallace, R. W. 1987. The origin of electrum coinage. American ogy 6:293–98. Journal of Archaeology 91:385–97. Barral, J., G. Favreau, and C. Lheur. 2011. Imiter: Morocco’s greatest Wallace, T. C., M. Barton, and W. E. Wilson. 1994. Silver and silver- silver mine. Mineralogical Record 42:107–35. bearing minerals. Rocks & Minerals 69:16–38. Beutell, A. 1919. Wachstumserscheinungen des kupfers, silbers und Warren, W. J., Jr., and E. Pedersen. 2003. Minerals of the Gilman goldes. Centralblatt für Mineralogie, Geologie und Paläontologie district and Eagle mine: Eagle County, Colorado. Rocks & Miner- 1919:14–29. als 78:298–323. Bischof, G. 1843: Einige Bemerkungen über die Bildung der Gang- Wilson, W. E. 1986. Famous mineral localities: The Silver Islet massen. Annalen der Physik und Chemie 136:285–97. mine, Ontario. Mineralogical Record 17:49–60. Blaha, F. 1957. Wachstum und Eigenschaften von Metallenfäden. Wilson, W. E., and C. S. Panczner. 1986. Famous mineral localities: Radex Rundschau 1957:882–90. The Batopilas district, Chihuahua, Mexico. Mineralogical Record Brandes, N. N., and P. T. Brandes. 2015. The famous silver mines of 17:61–80. Kongsberg, Norway. In 36th Annual New Mexico Mineral Sympo- Zawiskie, J. M. 2017. The mineral collection of Cranbrook Institute sium, 13–15 November 2015, Socorro, NM, 5–6. Socorro: New of Science, Bloomfield Hills, Michigan. Rocks & Minerals 92:38– Mexico Bureau of Geology & Mineral Resources. 45. ❑

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