AMETHYST MINING in BRAZIL by David Stanley Epstein
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AMETHYST MINING IN BRAZIL By David Stanley Epstein Brazil is currently the leader in overall ecause of its ready availability, modest cost, and production of amethyst. This article de- B attractive color, amethyst is currently one of the most scribes the author's visits to three of Bra- popular colored gemstones [figure 1).Fine amethyst histor- zil%most important mining areas: Mar- ically came from Russia's Ural Mountains and from the abd, Pan dArco, and Rio Grande do Sul. Idar-Oberstein area of West Germany, although both de- Each represents a different geologic envi- posits are now largely exhausted. Today, economic quan- ronment and, therefore, a variety of min- ing methods are used. In Maraha and Rio tities occur in Zambia, Mexico, and Uruguay, with lesser Grande do Sul, much of the amethyst is deposits in Australia, Sri Lanlza, India, Madagascar, South- heat treated to become citrine. west Africa, and the United States (Webster, 1983). The major source, however, is Brazil. Hundreds of tons of various grades of amethyst are produced there annually (419 tons in 1985), of which a small but important percentage is of cutting quality. Amethyst was discovered in Brazil early in the 19th century, by settlers from Idar-Oberstein (V R. Sudbaclz, pers. comm., 1987; Gonqalves, 1949); to date, mining claims have been filed in at least eight of Brazil's 27 states and territories. This article describes current mining of gem amethyst in three of the most important producing ABOUT THE AUTHOR areas-Maraba (which currently is producing the most Mr. Epstein is a gem sculptor and president of amethyst in Brazil), Pau dArco (which produces some of Precious Resources Ltda., Rua Dr. Joao Antonio, the finest material), and Rio Grande do Sul (which has the 287, Te6filo Otoni, Minas Gerais, Brazil. longest sustained production). These localities also pro- Acknowledgments: The author thanks the Bra- vide good examples of the occurrence of amethyst in three zilian D.N.P.M. (National Department of Mineral Products) and its department heads in Para and different geologic settings: as large veins in quartzite, as a Rio Grande do Sul for assistance in obtaining in- constituent of sedimentary alluvium, and as geodes in formation on and access to the amethyst mining basalt. areas. He also thanks geologist R. A. Correa Mar- tires for his help, patience, and exposure to per- This report is based primarily on the author's own sonal risk. Assistance was also provided by Dr. E. observations made during a fall 1987 visit to these three Fritsch, J C. Schmit, I A. Collyer, A. A. Mutter, H. M. Santos, A. Bortoluzzi, S. Klein, V. R. Sud- areas, which involved travel of over 12,000 lzm, plus back, 0. B. Ferreira, B. F. Filho, S. H. S. de Matos, information obtained from numerous discussions with B. F. de Alcontara, J. Miranda, 0. Miranda, local miners, amethyst dealers, and government geologists. M. do Carmo-Barreto, J. C. Miolo, K. Elawar, For each area, information is included on location and H. Elawar, and Bernd Munsteiner. Special thanks to Dr. J E. Shigley, without whose constant sup- access, occurrence of the amethyst, history of the deposit, port this work would not have been possible. mining methods, production levels, and quality grades of 0 1989 Gemological Institute of America the amethyst recovered [see table 1). Because almost all 214 Amethyst from Brazil GEMS & GEMOLOGY Winter 1988 Figure 1. This faceted 9-ct amethyst and the Rio Grande do Sul crys- tal cluster are representa- tive of some of the fine material that has come from Brazil. Jewelry cour- tesy of Silverhorn, Santa Barbara, CA; photo 0 Tino Hammid. citrine on the market today is produced by heat and town of Maraba (figure 2). Although the most treating amethyst, the treatment procedures prac- productive occurrence of faceting grade amethyst ticed at Maraba and Rio Grande do Sul are briefly being mined in Brazil today is that of Alto Bonito, described as well. Research done by Cassedanne all of the material from this general region is (1988 a and b) indicates that there are no signifi- commonly referred to by the name Marabi. cant differences in the gemology of amethyst from Maraba is easily reached from Belkm by regu- different areas of Brazil; general properties are larly scheduled airline. The hour-long flight is summarized in the accompanying box. almost entirely over dense, tropical rainforest that is interrupted occasionally by small, grassy clear- MARABA ings and meandering rivers. From Maraba, one Approximately 450 km south of Belkm, the capital must take an air taxi southwest to the ranch of the northern state of Para, lies the municipality (fazenda)on which the mine is located. A difficult Amethyst from Brazil GEMS & GEMOLOGY Winter 1988 215 BIOLOGICAL DESCRIPTION OF AMETHYST simply with a diffused light source ~uchas a light table. In more difficult cases, placing a. single polariz- jug filter between the light source and the amethyst will iw~8llym8ke the twinning visible. Finally, observatiw with the stone between crossed PO- lardds, pdblyeven with lotankrsion, should resolve the most-stubkprnme*. Detail if this technique are covered in .Crowningshield'et id., 1986, Brazil law twinning .bà not hew otwivod In any synthetic am&yst$tinlied to date, Condition and size Mining area Occurrence of crystals Colora Treatment Production Fracture fillings in Generally good Maximum tone of To citrine: buried in Approximately 9.6 quartzite condition; some 7 in best 19+-ct sand and heated tons of gem-quality free-standing, stones, tone 8 in by woodfire material produced some interlocked; 50 + -ct stones in 1986 individual crystals up to 15 kg in weight, 50 cm long Pau dArco Alluvial deposits Partially eroded; Maximum tone of To lighten color, Approximately 7 from 300 grams to 10 in 1-ct stones heated in test tube; tons of all qualities 40 kg never turns to produced annually citrine in 1985 and 1986 Rio Grande do Sul Geodes inside Pyramidal crystals; Maximum tone of To citrine: heated Approximately 19 basalt up to 10 cm long 7 in 10-ct stones in oven tons of gem-quality amethyst and heat- treated citrine shipped legally through Rio Grande do Sul in 1986 'Based on lone scale used by author in the Held (see figure 5) 216 Amethyst from Brazil GEMS & GEMOLOGY Winter 1988 r^, Rio de Janeiro Figure 2. Brazil is now the most important source of amethyst in the world. This map shows the location of the Alto Bonito (Marabd) and Pau d'Arco amethyst deposits in the state of Para, and the M and Santa Maria workings in the state of Rio Grande do Sul. Artwork by Peter Johnston. one-hour drive by truck (a "taxi" service provided Occurrence. Alto Bonito lies within the broad by the landowner) leads to the hillier region of Carajas mineral province [Collyer and Martires, Serra dos Caracas, where the amethyst is mined. 1986).which also includes the famous Serra Pelada The approximate geographic coordinates of the gold deposit. The amethyst occurs in a series of Alto Bonito amethyst deposit are 5"15'S and sedimentary and extrusive volcanic rocks of lower 50'30' W. Travel is advisable during the drier Proterozoic age (approximately 1.7 to 2 billion months. June to November, when temperatures years old). Specifically, it is distributed irregularly range from 18' to 40° (64' to 104¡F) in veins and cavities in highly fractured and folded Amethyst from Brazil GEMS & GEMOLOGY Winter 1988 217 cause the fragments were of poor quality, and no one in the area had any knowledge of amethyst, this find remained unexploited for over a year until a prospector from Bahia, Manuel Xavier, saw the material and recognized its cutting potential. Xavier began the first amethyst diggings in the Marabi area. These early workings were simple pits that reached a depth of only 2 to 3 m and were soon exhausted. Subsequently, Jose Miranda Cruz, the eldest of six Miranda sons, initiated a more orga- nized exploration and recovery of amethyst. He built houses for the miners, and later a general store, school, and other facilities to sustain a community of several hundred persons. He also initiated the use of mechanized equipment so that the worlzings could be extended underground. At Alto Bonito there are currently 22 barrancos (shafts or tunnels] spread over an area of approx- imately 500 m2. Each has numerous owners and partnerships, who pay 10% of the value of the recovered amethyst to the landowners for the opportunity to mine. Mining Methods. The majority of the mining is done with piclzs, shovels, buckets, jaclzhammers, and occasionally small amounts of dynamite. Vertical shafts and horizontal tunnels are exca- Figure 3. Both white quartzite and reddish vated to follow the veins of amethyst, and are quartzite are evident in this photo of an ame- reinforced with timbering taken from the sur- thyst-mining operation at Alto Bonito, near rounding forest. Electricity for lighting and ven- Marabk, in the state of Pard, tilation systems are added as needed and as money is available. During my visit I was able to explore a number of these workings and experience some of layers of quartzite, a tough, siliceous, meta- the trauma and excitement of the amethyst miner morphosed sedimentary rock. Two kinds of firsthand. quartzite, which differ primarily in color, can be To reach the first level of the Paulinho bar- recognized in the field (figure 3). One is white or ranco, I was lowered by rope 20 m into almost total light colored, and the other is more reddish due to darkness. I then walked about 5 m along a tunnel staining by hematite and other iron oxides.