GEM RHODOCHROSITE from the SWEET HOME MINE, COLORADO by Kimberly Knox and Bryan K

GEM RHODOCHROSITE FROM THE SWEET HOME MINE, COLORADO By Kimberly Knox and Bryan K. Lees Massive banded rhodochrosite has nusual gemstones have increased markedly in long been used for carvings and other U popularity over the last several years. This trend ornamental objects. Although intense has been stimulated not only by the availability red transparent rhodochrosite crystals of these materials, but also by new cutting techniques and of remarkable size have been known in the creative efforts of innovative jewelry designers willing to Colorado since 1895, not until recently integrate unusual materials into their works. Critical were mining techniques developed to acknowledgment and distinction for such materials are recover them economically. These new mining techniques have combined earned through such venues as the AGTA Cutting Edge and state-of-the-art equipment and tech- Spectrum Awards. Faceted rhodochrosite, which was recog- nology to detect and extract large, fine- nized at the 1996 Cutting Edge competition, is one of the quality rhodochrosite specimens and most exciting new gem materials to appear as cut stones gem rough. Although rhodochrosite is and in jewelry, following years as one of mineral collectors’ a soft mineral, faceted rhodochrosite most sought-after specimen materials (figure 1). can be set into jewelry provided it Although rhodochrosite is softer than almost all other receives special handling and consider- gemstones (even opal), it is harder than some, such as pearl. ation with respect to wear. Faceted Properly set and cared for, rhodochrosite can be made into rhodochrosite can be readily separated outstanding pins, pendants, tie ornaments, and necklaces. from possible imitations on the basis Until recently, rhodochrosite was primarily available as of standard gemological testing. a pink opaque massive material, with the irregular curved or concentric pattern of gray or white banding that is character- istic of its stalactitic or nodular formation; typically, it is fashioned into cabochons, beads, or ornamental carvings (figure 2). With the recent redevelopment of the Sweet Home mine near Alma, Colorado, large (one over 14 cm, but averag- ing 2.5 cm), fine specimens of transparent-to-translucent rhodochrosite crystals, as well as small amounts of faceted rhodochrosite, have entered the gem and mineral trade. The faceted gems are usually deep, intense pink to red, typically modified by orange, and completely transparent. ABOUT THE AUTHORS Colorado has been known as a source of fine Ms. Knox, a Graduate Gemologist and artist, is the owner of Golden Pacific Arts, 520 Fifth Ave., San rhodochrosite since the 1800s, and the Sweet Home has Diego, California 92101. Mr. Lees, a geological been the most significant producer since 1895 (Jones, 1986). engineer, is president of Sweet Home Rhodo, According to Sinkankas (1997, p. 408), the mine is “known Inc., and owner of The Collector’s Edge, P.O. Box 1169, Golden, Colorado 80402. worldwide for its unmatched crystals of transparent, vivid red rhodochrosite. .” Please see acknowledgments at end of article. Although there have been and still are other sources of Gems & Gemology, Vol. 33, No. 2, pp. 122–133 gem rhodochrosite—for example, South Africa’s Kalahari © 1997 Gemological Institute of America Desert and the Pasto Bueno and other districts in Peru— 122 Sweet Home Rhodochrosite GEMS & GEMOLOGY Summer 1997 Figure 1. Long a favorite of mineral collectors worldwide, some rhodochrosite is now being faceted and even set in jewelry. This 5 × 6 cm rhodochrosite crystal on tetrahedrite and the 21.50 ct cushion-cut rhodochrosite are both from the Sweet Home mine, near Alma, Colorado. Courtesy of The Collector’s Edge, Golden, Colorado. Photo © Harold & Erica Van Pelt. their production has been irregular. The Sweet 1975). Dr. Mansfeld hoped to sell large quantities to Home remains the single most important source of institutions of applied arts as a carving material. fine rhodochrosite specimens and faceted stones. Although his efforts to integrate rhodochrosite into This article describes the history of rhodo- the applied arts were unsuccessful, he did popular- chrosite and the geology of the Sweet Home mine. ize the massive, opaque form of this stone (Shaub, Also discussed and illustrated are the novel, con- 1972). temporary mining techniques developed by Sweet Massive rhodochrosite actually occurs in many Home Rhodo, Inc. The results of a basic gemologi- localities in addition to Argentina. In Europe, it is cal analysis of eight Sweet Home faceted rhodo- found in Romania, Yugoslavia, and Germany; in chrosites are presented, along with identification Australia and its environs, it comes from New criteria. Last, cutting and setting techniques specific South Wales, Victoria, South Australia, and to rhodochrosite are described in detail. Tasmania (Clark, 1980); and in Mexico, it is known from the Cananea and Santa Eulalia mining dis- HISTORY tricts (Jones, 1978). Rhodochrosite was first described in 1813 by J. F. L. However, the single-crystal form of this mineral Hausmann, using material from Kapnik, Transyl- is relatively rare. In 1887, Dr. George F. Kunz of vania. Dr. Franz Mansfeld is credited with introduc- Tiffany & Company reported finding gem-quality ing North America and Europe (around 1934) to rhodochrosite in Colorado, “the first locality to "Inca Rose," the massive rhodochrosite found in yield crystals of such magnitude and transparency.” abundance in Argentina’s Catamarca Province A specimen of Sweet Home rhodochrosite that was (Shaub, 1972). Reportedly the mine was once acquired by the second author in 1987 bore a label worked by Incas for silver and copper (Webster, from the American Museum of Natural History; Sweet Home Rhodochrosite GEMS & GEMOLOGY Summer 1997 123 Figure 2. Traditionally, the rhodochrosite seen in the gem trade is the gray- or white-banded massive pink material that has been found in large quantities in Catamarca, Argentina. It is used primarily as beads and cabochons or for carvings. This photo shows some finer examples of this material. The two carvings are accompanied by slices of rhodochrosite taken from large stalac- tites (similar to the smaller stalactite section shown here). The faceted stones, (5.88 and 17.43 ct), which are from the Hotazel (South Africa) and Sweet Home mines, are included to give some idea of the differences in size between the massive opaque and transparent materials. From the collection of Michael M. Scott; photo © Harold & Erica Van Pelt. this specimen was traced back to a donation by cm have been produced from the Uchucchacua Tiffany and Company during the 1890s. In addition mine, in Peru’s Oyon Province. However, produc- to the Sweet Home mine, the famous American tion from the Kalahari region has been irregular and Tunnel gold mining project of the 1950s in the crystals are small. Pasto Bueno produced fewer Silverton, the Climax molybdenum and John C. than two dozen “outstanding” rhodochrosite speci- Reed (Alicante) mines (Jones, 1993), and the Moose mens, and the Uchucchacua crystals, like those (Pleasant Valley) and Mickey Breen (Uncompahgre from Kalahari, are small (Crowley et al., 1997). Gorge) mines (Sinkankas, 1997) have also produced An active silver mine since 1872, the Sweet rhodochrosite in Colorado. Home (then known as the Home Sweet Home In 1974, gem-quality rhodochrosite was discov- mine) holds one of the earliest U.S. mining patents, ered at the N’Chwaning and Hotazel mines in No. 106, granted under the General Mining Law of South Africa’s Kalahari manganese fields (Wight, the same year (“Specimen mining,” 1994). The 1985; figure 3). Around the same time, a few superb, mine was operated intermittently almost 90 years, large samples of gem-quality rhodochrosite emerged until the 1960s, and extensive tunnels were driven from the Huayllapon mine in the Pasto Bueno dis- to exploit the mine’s silver reserves. During that trict, Pallasca Province, Peru (Clark, 1980; Crowley period, rhodochrosite was regarded as a passing et al., 1997; figure 4). Since 1985, transparent “deep curiosity, and most was discarded on the dumps. raspberry-pink to strawberry-red” crystals up to 2.5 Leonard Beach, owner of the Sweet Home mine 124 Sweet Home Rhodochrosite GEMS & GEMOLOGY Summer 1997 since about 1961, steadfastly maintained that many valuable rhodochrosite specimens were waiting to be retrieved. For over 25 years, through lectures and a circulating mining prospectus, he kept that idea alive. In 1966, following an unproductive silver- exploration effort, contractor John Soules decided to look for rhodochrosite crystals in one of the mine tunnels. A mine map from the 1920s showed a zone where a rich red seam of rhodochrosite had been uncovered but abandoned. This zone was opened and a superb specimen was uncovered (illustrated in Bancroft, 1984, pp. 60–61); it is now in the collection of the Houston Museum of Natural Science. In 1977, Beach leased the mine to Richard Kos- nar and John Saul, owners of the Intercontinental Mining Corporation (Sinkankas, 1997). They uncovered several productive pockets. However, better tools and collecting techniques had to be developed before major pieces could be recovered undamaged. Most recently, in 1991, the Sweet Home Rhodo, Inc., mining company was founded by a group of investors who were intrigued by Leonard Beach’s concept of a stand-alone specimen-mining effort. Figure 3. Another source of fine transparent They spent a quarter of a million dollars to lease and rhodochrosite crystals is the N’Chwaning mine in rehabilitate the old mine in order to put it back into northern Cape Province, South Africa. This cluster production—this time not for silver, but for of red scalenohedral rhodochrosite crystals from rhodochrosite specimens. In 1992, the Sweet Home N’Chwaning measures 9.5 cm. However, crystals produced the largest specimen known from this over 3 cm from this region are extremely rare. locality, the Alma King (figure 5), which contains a From the collection of the Houston Museum of rhodochrosite crystal measuring 14.25 cm on a side Natural Science; photo © Harold & Erica Van Pelt.

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