New Mexico Mineral Symposium — Abstracts

The Sneffels mining district is located approximately 8 mi south of Ouray, Colorado, in Imogene, Sidney, Silver Lake, and Yankee Boy Basins. The district is situated in the heart of the San Juan Mountains and in rugged and beautiful mountainous terrain at elevations over 13,000 ft.

In the 1870s and 1880s, the basins were the scene of intense mining activity and promotions, both miners and promoters hoping to make a fortune on the newly discovered silver deposits. Mines named the Minne B, Circassian, Eldorado, Ruby Trust, Yankee Boy, and Black Diamond sprang to life. Most of these mines were short-lived, lasting only a few years, but a few lingered on until the silver panic of 1893 shut down the remaining mines.

Thomas Walsh discovered rich gold ore in a quartz-sulfide vein in Imogene Basin in 1896. The operation was named the Camp Bird mine and made Walsh a millionaire many times over. The mine operated for almost 100 yrs and produced more than 1.5 million ounces of gold.

Leasers again resumed sporadic activity on the silver veins in the 1920s and 1930s, but production was small. In 1986 a Utah mining group leased the Eldorado group of claims, and an exploration drift was driven on the Eldorado vein. The drift encountered two small silver-bearing orebodies that were mined and produced a variety of fine crystallized minerals.

The silver-bearing veins of the basins occur in Tertiary-age San Juan tuff and the Stony Mountain gabbro-granodiorite intrusion. The veins can be as much as 5 ft wide, and most have a general northwest trend.

Of interest to the mineral collector are a number of mineral species found as well-crystallized microcrystals to thumbnail specimens. Ore minerals found to date include native gold, native silver, polybasite, acanthite, pyrargyrite, tetrahedrite, galena, sphalerite, and chalcopyrite. The gangue minerals in the veins include pyrite, marcasite, arsenopyrite, quartz, barite, rhodochrosite, kutnohorite, dolomite, siderite, and calcite. Of special interest are the globular inclusions of pyrargyrite and tetrahedrite in clear crystals of quartz and barite.