New Mexico Mineral Symposium — Abstracts

Connoisseurs of wulfenite probably do not think of Colorado as a noteworthy state that has produced fine specimens of wulfenite. Surprisingly though, fine microcrystals of wulfenite have been found in a variety of ore deposits throughout the state. A good part of the Colorado wulfenite localities does not compare with those in Arizona and New Mexico, but microcrystals of wulfenite and associated minerals make interesting and rare additions to the micromounter's collection.

The majority of documented wulfenite finds have been made in the last 35 yrs because of new mining operations or as new discoveries in abandoned mines.

The first mention of wulfenite in Colorado was made in 1878 by F.M. Endlich in his min¬eralogical report in the Tenth Annual Hayden Survey Report. Other early reports of wulfenite in Colorado include the Central City district, the Silver Cliff district, and the Breckenridge district.

The creme de la crème wulfenite locality for Colorado is the Sherman tunnel, located east of Leadville at the base of Iowa Amphitheater at an elevation of 12,200 ft. The deposit was discovered in 1968, and the Sherman tunnel was started in 1970.

Strong oxidation and enrichment in parts of the irregular orebodies in the Leadville Dolomite have formed a large variety of secondary minerals including malachite, azurite, rosasite, aurichalcite, cerussite, smithsonite, hemimorphite, wulfenite, and native silver. All of the minerals occur as microcrystals in various associations.

The mines of the San Juan Mountains of southwestern Colorado have produced some of the best microcrystals of wulfenite that have been found in the last 30 yrs; before that wulfenite was not mentioned as occurring in the San Juans.