New Mexico Mineral Symposium — Abstracts

Turquoise Mountain is in the Eureka mining district in the Little Hatchet Mountains, Grant County, New Mexico. It is immediately west of the ghost town of Old Hachita. Turquoise Mountain is on Bureau of Land Management land, and New Mexico State land is present to the south and east. Access to the area is good, but four-wheel drive vehicles are recommended as sections of the road are not maintained.

Indians first worked the deposits for turquoise hundreds of years ago. In the 1880s mines in the district were worked for gold, silver, and copper, but none of these deposits proved of great eco¬nomic importance. In 1885 miners began working the district for turquoise. Mining lasted until 1888 and was restarted in 1892 but with little result. In 1908 extensive mining started, but it only lasted a few years. Fine sky-blue material was reported to have come from a number of claims (Carter, 1965).

The turquoise deposits in the Little Hatchet Mountains have reportedly produced some large pieces of turquoise. Sinkankas (1997) described a 160 lb piece that was extracted in 1926 from a mine in the Hachita Mountains. This piece was carved into a scene depicting a pueblo and its occu¬pants and was exhibited at the Tucson Gem and Mineral show in 2001 by Freedland's Jewelry of Tucson, Arizona. The piece weighed 121 lb after carving and was considered to be the largest in the world (Tucson Show Web site, 2001).

Carson (1975) described the area in detail from a collector's standpoint. Whereas Turquoise Mountain has been the focus of turquoise activity in the Eureka mining district, showings that are not profitable for large-scale commercial mining yet attractive to collectors, surround the area around Turquoise Mountain. The Azure mine, which is not to be confused with the Azure mine in the Burro Mountains turquoise district, is located on top of Turquoise Mountain and has produced high-grade material. The Cameo mine, about 1 mi northwest of the northeast end of Turquoise Mountain, was developed by a vertical shaft. The Cameo mine is one of the oldest in the region based on the number of stone tools found, and the material is similar to that of the Azure mine. The Galilee mine, about 0.5 mi southwest of Turquoise Mountain, was worked by a large pit and produced from two prominent veins. The Aztec mine, named because of its prehistoric workings, is about 1.5 mi southwest of Turquoise Mountain. The Aztec mine was worked by an adit, and the turquoise is present in seams as nuggets scattered throughout the rock. The turquoise here is soft and pale and sometimes fades under exposure. Darker blue turquoise is reported to occur in the American Turquoise mine, which is a few hundred yards west of the Cameo mine. This claim was worked from both an open pit and a shaft. The turquoise here is quite hard and is predominantly pure turquoise. Carson (1975) noted that these sites and most of the other claims in the area are patented, but that collectors would encounter no entry problems as long as property rights are respected. During a site visit in August of 2000, no indications of claims stakes or indications of other restrictions to collecting for personal collections were observed in the area of Turquoise Mountain.

Geologic mapping by Zeller (1970) indicates that Turquoise Mountain consists of a hydrother¬mally altered monzonite stock and andesite and andesite breccia of the Hidalgo volcanics. The Hidalgo volcanics are believed to be early Tertiary in age, indicating that the monzonite stock may also be early Tertiary. Where exposed, the stock is generally iron stained due to the abundance of disseminated pyrite in the unweathered rock. Much of the rock has been altered to clay minerals, and this is immediately apparent from the fine-grained, white character of the rock. Turquoise is present in altered rocks along the borders of the stock.

Collecting of turquoise at Turquoise Mountain is relatively easy, and loose pieces can be found on the surface of trench floors and in piles along the sides of old equipment trenches and cuts. Most of the turquoise in the walls of trenches and cuts is present as veinlets and along fracture fill¬ings. Color ranges from sky blue to light green. A breaker bar is useful for breaking out large slabs, and a flat chisel with a hammer can be used to split apart smaller pieces. Areas with veinlets on the surface should be explored deeper with a breaker bar, as collecting in the district has undoubtedly removed the bulk of the loose turquoise on the surface.

References:

1. "A big piece of blue," in Snapshots from Tucson, 2001 [database online] (Tucson Show Web site) [cited October 4, 2001] available from http: / / www.tucsonshow.com/reports/tucson2001/p13.shtml.
2. Carson, Xanthus, 1975, Turquoise in New Mexico: Rockhound, v. 4, no. 2, March???April.
3. Carter, M.D., 1965, Gem materials, in Mineral and water resources of New Mexico: New Mexico Bureau of Mines and Mineral Resources, Bulletin 87, pp. 267-276.
4. Sinkankas, John, 1997, Gemstones of North America: Geoscience Press, Inc., V. III, Tucson, Arizona, 526 pp.
5. Zeller, Robert A., 1970, Geology of the Little Hatchet Mountains, Hidalgo and Grant Counties, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Bulletin 96, 26 pp.