New Mexico Mineral Symposium — Abstracts

The Camp Bird mine, located 6 miles southwest of Ouray, Colorado, was discovered by Thomas F. Walsh in 1896. Under Walsh's management, the Camp Bird mine was developed into one of the most profitable and famous mines in Colorado and made Walsh a millionaire many times over.

Rocks in the Camp Bird mine area consist of Paleozoic and Mesozoic sediments that have been partially eroded. The Tertiary Telluride Conglomerate was deposited on the peneplained surface and is the host rock for the Pb-Cu-Zn replacement orebodies. Later volcanic eruptions from a series of central-vent volcanoes deposited rhyodacitic ash and lava flows on the Telluride Conglomerate and formed the Tertiary San Juan Tuff and Silverton volcanic series.

All of the gold production of the Camp Bird mine has come from the Camp Bird vein, which strikes east-west and dips 70° south. Early-day production was mainly Au-Ag-Cu ores, but as mining progressed deeper, the gold values diminished and changed to Ag-Pb-Cu-Zn ores.

Three stages of mineralization make up the compound Camp Bird vein. The first stage of vein formation was the quartz-sulfide component, which consists of quartz, galena, chalcopyrite, sphalerite, and rarely tetrahedrite. Accessory minerals include pyrite, calcite, chlorite, rhodonite, rhodochrosite, fluorite, ankerite, and scheelite. The second stage of vein formation was the gold-quartz breccia component, which consists of quartz, gold, minor petzite, and locally, small amounts of sulfides. In the deeper levels of the mine, appreciable specularite hematite is associated with the gold stage. The third and last stage of vein formation was the bull quartz stage, which is barren of ore minerals and usually forms massive veins, which sometimes show cockscomb structure. Vugs are numerous and contain milky white quartz crystals up to 4 inches long.

During the 1970s most of the ore mined was from Pb-Cu-Zn replacement orebodies along the Orphan and Gordon veins at the base of the Telluride Conglomerate. Galena, chalcopyrite, and sphalerite were the primary ore minerals and replaced the matrix, pebbles, and cobbles that made up the conglomerate. Accessory minerals include quartz, epidote, calcite, pyrite, barite, fluorite, and rhodochrosite.

Over the years, the Camp Bird mine has produced hundreds of fine mineral specimens. Exceptional specimens of native gold and quartz crystal groups have come from the Camp Bird vein, whereas exceptional crystal groups of galena, sphalerite, and chalcopyrite associated with quartz, epidote, and calcite have been recovered from the replacement orebodies. In June 1987 a vug was discovered in the Camp Bird vein that produced the finest scheelite crystals ever found in Colorado.