New Mexico Mineral Symposium — Abstracts

The Zuni Mountains near Grants, in northwestern New Mexico, are not well known as a mineral-collecting locality even though some nice specimens of fluorite, barite, and copper oxides have been found there. The eastern mountains contain Precambrian veins and Paleozoic stratabound sedimentary copper deposits that have produced more than 30,000 lbs of copper, 260 oz of silver, and 2 oz of gold. However, the most important production in this area came from veins that produced more than 192,000 tons of fluorspar ore from 1909 to 1962. Thus, the eastern Zuni Mountains contain one of the largest fluorspar districts in the state.

Fluorite with subordinate amounts of quartz, calcite, and, rarely, barite and galena occurs in veins up to 7 ft wide and several thousand feet long. The veins typically intrude Precambrian gneissic granite, although a few fluorite veins intrude Paleozoic sedimentary rocks. The veins are concentrated in two major areas, one near the mines in sections 21 and 27 and the other at the Mirabel mine in Diener Canyon.

Blue, purple, green, and colorless cubes of fluorite up to 1/2 inch across are common in both areas. Specimens of small stacked fluorite cubes sometimes exhibit an iridescent or pearly luster. Massive, banded, blue and green fluorite provides nice slabbing material and can be found in veins near the sections 21 and 27 mines. Some banded fluorite also occurs at the Mirabel mine. Clusters of bladed pink- to salmon-colored barite, occasionally with fluorite, occur near the Mirabel mine. Some of the specimens near the Mirabel also contain blades of malachite with fluorite and barite.

Many of the fluorspar deposits occur on national forest land and are readily accessible to the public. Mineral collectors should be careful, however, because many of the underground workings are extremely hazardous. Good material can be obtained from mine dumps and shallow open trenches.