New Mexico Mineral Symposium — Abstracts

Fluorite occurs in a wide variety of geologic conditions throughout Colorado: in pegmatites, in hydrothermal veins, and in lead-silver deposits. It is found most often as simple cubes or octahedrons, sometimes growing to 10 cm on edge. Crystals of a lavender or purple color are the most common, but fluorite in Colorado also can be lemon yellow, light green, dark green, blue, colorless, or zoned purple-green or purple-lavender combinations.

In the pegmatites of the Pikes Peak granite, fluorite is found in association with amazonite, smokey quartz, albite, and goethite. Cubes to 10 cm have been reported, but more commonly grow to about 4 cm. In the huge molybdenum deposit at Climax, fluorite occurs as complex octahedrons of a green or bluish-green color, typically with purple zonations, in association with rhodochrosite, quartz, and pyrite. In the central part of the state, at Mt. Antero, fluorite forms large octahedrons of dark purple or green in association with aquamarine, mica, phenakite, and microcline. In the Cresson mine at Cripple Creek, lemon-yellow fluorite has been found. It is also found there as massive, earthy-textured, purple material. In Unaweep Canyon, Mesa County, at the Nancy Hanks mine, fluorite forms lime-green octahedrons consisting of plates with individual crystals approximately 10 mm across associated with amethyst. In the San Juan Mountains of southwestern Colorado, fluorite occurs in many locations as pale- to medium-green octahedrons in association with drusy quartz, rhodochrosite, and barite. Notable occurrences in this region include the Sunnyside mine at Silverton, the Ransom mine at Eureka, the Thistledown mine near Ouray, and the Gertrude and Grizzly Bear mines, also in Ouray County.

Fluorite also occurs at many other localities through Colorado, including the Bonanza mining district, where it forms lime-green octahedrons associated with rhodochrosite at the Eagle mine (not to be confused with the mine of the same name at Gilman), in the Northgate district, and in the Central City district. In these and other localities fluorite forms large well-formed single crystals and attractive clusters.