This spectacular crystal of Rhodocrosite (MnCO3), known as the “Alma King” measures 14 cm x 16.5 cm. This perfect rhombohedron was recovered in the wall of a narrow pocket on a matrix of white, needle clear Quartz, blue Fluorite, black Sphalerite and Tetrahedrite, brassy Chalcopyrite and pale yellow Calcite. The “Alma King” was collected in 1992 from the Sweet Home Mine, which is located about 144 km southwest of Denver, Colorado, near the small old mining town of Alma. Sweet Home Mine was originally opened as a Silver mine in the 1870’s and was mined until the 1960’s. Throughout the mine’s lifetime, nice Rhodochrosite specimens were found along with the silver ore, but not used commercially. In 1991 the mine reopened as a Rhodochrosite specimen mine.
Rhodochrosites from the Sweet Home Mine are gem-quality crystals because of their translucent cherry-red color, which is due to the relatively low amount of iron, magnesium and calcium impurities. Note that when calcium, magnesium, and especially iron ions substitute for manganese, a pink color will result. Many experts acclaim the “Alma King” as the finest and most valuable mineral specimen ever mined in North America. Rhodochrosite became the Colorado State Mineral in 2002.
The “Alma King” can be seen in the permanent display in the Coors Mineral Hall at the Denver Museum of Nature and Science, Denver, Colorado.
(Above photo is from Wikipedia, the free encyclopedia.)
Occurances of Rhodocrosite are numerous and include the famous Sweet Home Mine, Alma, Park County and American Tunnel, Silverton, Colorado; Butte, Montana; the mines of Franklin, New Jersey; Humboldt Mine, Cochise County, Arizona and many sites in California, USA. Also found in Catamarca, Argentine; Huaron Mine and several mines in Ancash Department, Peru; Kara oba, Kazakhatan; Sacrimb, Transylvania, Romania; Cornwall, England; Harz Mountains, Germany; Tsumeb, Otavi, Namibia; Santa Eulalia and Magdalena, Mexico; N'Chwanging Mine, Hotazel, South Africa; Mont Saint-Hilaire, Quebec, Canada and many other localities from around the world (See Stamps. below, from different countries featuring Rhodocrosite).