New Mexico Mineral Symposium — Abstracts

During the last decade a number of important mineral discov-eries have been made in active and inactive mines in the San Juan Mountains. Some of the minerals collected had not be reported previously from the area, while other discoveries consisted of good to spectacular crystallized groups of the more common minerals that occur in the area mines.

The Eldorado mine, located in Yankee Boy Basin in the Sneffels mining district, is a small silver mine that was first worked in the 1870's. In 1985, there was renewed interest in the mine and a new drift was driven below the old workings. Drifting on the vein disclosed small ore shoots that produced a variety of exotic and beautiful silver sulfosalts and gangue minerals. Most of the minerals occur as well-crystallized microspecimens.

Proustite occurs as beautiful red translucent crystals perched on quartz crystals. It also occurs as transparent deep-red globular inclusions in wafer-thin, colorless, tabular barite crystals. Pyrargyrite occurs as very dark red crystals associated with crystallized chalcopyrite and wires of native silver. Polybasite and pearceite occur as black, tabular, pseudohexagonal crystals scattered on quartz crystals. Miargyrite occurs as thick, tabular, iron-black crystals in quartz vugs with pyrite crystals. Other minerals that occur with the sulfosalts are galena, siderite, arsenopyrite, and rhodochrosite.

The Camp Bird mine, located 5 miles southwest of Ouray, is one of the more famous gold mines of Colorado. During the last four years, rehabilitation and renewed mining has produced a number of specimens for the mineral collector and micromounter. Of interest to the micromineral collector is the occurrence of crystallized gold in quartz vugs. The gold occurs as delicate wires and distorted crystals perched on quartz crystals. Petzite also occurs in the vugs as single, shiny-black, complex crystals on quartz and as crystals perched on crystallized gold.

The most fabulous find to date at the Camp Bird mine has been a large fluorite vug containing hundreds of scheelite crystals. The crystals range from light gray to dark brown, and individual crystals are from 1 mm to 2 cm on edge. The crystals are dipyramids with the most common form being (011) and (112). The dipyramids and groups occur on and in a matrix of sugary- textured, colorless fluorite. Other minerals that occur in the vug are chalcopyrite, pyrite, sphalerite, galena, calcite, and quartz. Secondary minerals present are ferrimolybdite, gypsum, and dickite.

The Brooklyn mine is a small gold mine located in Brown's Gulch about 6 miles northwest of Silverton, Colorado. The mine was first worked about 1900 and has since had sporadic produc¬tion. From 1978 to 1981 small gold orebodies were mined on 1 and 2 level of the mine that produced beautiful specimens of leaf and wire gold. In 1980 a small orebody was mined on 2 level that produced some rare and unusual minerals. Native mercury, cosa¬lite, and tetradymite, along with native gold, apatite, and monazite were collected.

Other finds in the San Juan Mountains in the last ten years include wulfenite at the Bandora mine near Silverton, anatase on quartz at the Ores and Metals mine near Ouray, and large milky quartz crystal groups at the Ohio mine near Ouray.