Abstract Gems & Gemology, Spring 2013, Vol. 49, No. 1

Copper-Bearing Minerals of Colorado

Between 1868 and 1922, Colorado produced almost 260 million pounds of copper. Nearly 100 million pounds came from the Leadville district, with another 50 million mined in San Juan County. During the 20th century, the Gilman district surpassed Leadville in total copper production, yielding more than 210 million pounds. Total Colorado production prior to 1958 reached 585 million pounds.

In this article, 106 minerals from the Colorado Mineral Belt (COMB) are listed and 39 are discussed in the text. The Eagle mine in the Gilman district is probably Colorado’s most prolific producer of mineral specimens. Gilman pyrite, sphalerite, chalcopyrite, siderite, barite, and galena are found in collections all around the world. The Sweet Home mine in Buckskin Gulch, a source of world-famous rhodochrosite, is also well known for fine specimens of two copper-bearing minerals, bornite and tetrahedrite. The Creede mining district is one of the most extensively studied mineral deposits and volcanic areas in the country. A detailed study of the Creede ore deposits has been conducted in an attempt to develop a model for epigenetic precious-metal deposits. Summitville is well known as the source of the state’s finest covellite specimens. The Good Hope mine is the type locality for four copper-bearing tellurides: rickardite (Cu3-xTe2), weissite (Cu2-xTe), vulcanite (CuTe), and cameronite (AgCu7Te10). Turquoise was mined from the King mine deposit in Conejos County and from the Chief mine in the St. Kevin district of Lake County.

The state of Colorado has produced some significant copper-bearing mineral specimens. Most of its copper minerals are sulfides and sulfosalts, with chalcopyrite the most common copper-bearing mineral.

Abstracted by Guy Lalous