Minerals from the lesser mines of the San Juan Mountains, Colorado

The San Juan mountain range is located in the southwest quadrant of Colorado at the end of the Colorado mineral belt. These mountains are relatively young by geologic standards, being about 15-20 m.y. old. With the exception of the Red Mountain mining district's breccia pipes, massive quartz veins contain gold, silver, pyrite, galena, fluorite, barite, sphalerite, and less common species such as rhodochrosite, hübnerite, chalcopyrite, and tetrahedrite. These species commonly occur in large, well-formed crystals, generally as much as 2 in long, but sometimes found as long as 12 in.