New Mexico Mineral Symposium — Abstracts

COOKE'S PEAK DISTRICT—Cooke's Peak is the highest point in Cooke's Range, approximately 24 mi northeast of Deming. It is reached by taking US-180 north from Deming, then turning east on NM-26 to the Florida Siding where a dirt road leads north to Cooke's Peak. Access is via a locked gate with permission from the rancher. The last few miles require four-wheel drive.

The greatest activity at Cooke's Peak took place from 1880 to about 1905 in the San Jose district on the west side, the Cooke's Peak district on the east side, and the Old Hadley near the southeast base. During that time the three districts annually produced about 1.5 million lb of lead and 6,000 oz of silver (Jicha 1954). The most productive claims, the Desdemona, Othello, and Summit Groups, were located in the Cooke's Peak district and accounted for $2,350,000 of the total production up to 1910 (Lindgren et al. 1910). The mining camp on the east slope grew into a flourishing town named Cooks (note the different spelling), which boasted a post office, school, mercantile, and saloon (Couchman 1990). By 1910 the richest oxidized ores were depleted, although mining continued on a smaller scale for lead, zinc, silver, and copper until 1953 (Jicha 1954). By then Cooks had dwindled to a ghost town and has since disappeared.

Cooke's Peak consists of faulted sedimentary rocks intruded by a Late Cretaceous or early Tertiary granodiorite stock. Some Tertiary volcanics crop out near the base. Orebodies occur as fissure fillings and modified mantos in Silurian limestone. Primary minerals galena and sphalerite are deeply oxidized to form the principal ore minerals cerussite and smithsonite (Lindgren et al. 1910; Jicha 1954). Lesser amounts of copper and a good deal of fluorite are also present.
Most of the collectable microcrystals are secondary lead and zinc minerals but also include copper secondaries and fluorite. The appeal of these common species lies in their variety of colors and crystal habits:

• Copper minerals are sparse, aurichalcite and malachite being somewhat more abundant than azurite and rosasite.
• Cerussite occurs as milky or clear elongate crystals, v-twins, reticulated groups, and most desirably as peach-pink twinned crystals.
• Fluorite microcrystals are common as colorless cubes, frequently modified by octahedron or dodecahedron faces, and sometimes zoned with purple. Pale to deep purple cubes or octahedrons line some pockets.

Cooke's Peak is the type locality for plumbojarosite, found as aggregates of yellow, brownish, or greenish platy crystals. A sample of identical crystals grading from golden yellow to dark brown thought to be jarosite was identified as corkite. Tiny opaque-white hexagonal prisms associated with similar crystal aggregates proved to be pyromorphite. These are the only phosphates found to date. Pyromorphite can be sight identified, but corkite and plumbojarosite can only be distinguished by analysis.

The principal mineral of interest is wulfenite. It occurs in a great variety of habits including prismatic, tabular, pyramidal, and blocky and ranges in color from almost colorless grayish to yellow, orange, many shades of brown, and even green. Brown wulfenites are usually associated with or perched on clear or color-zoned fluorite.

OLD HADLEY DISTRICT—The Old Hadley (Graphic) district is located a short distance southeast and on the southern approach to the Cooke's Peak district. The district is a small one, covering 1 mi east to west and 2.5 mi north to south. The area, at 5,600 ft elevation, contains perhaps 15 mines and prospects of which three probably had significant production. Predominate rock types include Tertiary pyroxene andesite of the Macho series and quartz latite. An intrusive granodiorite stock, from which the district's mineralized fluids were derived, is located 2,000 ft west of the main vein systems. Fissure veins, made up of barite and quartz gangue strike generally north-northeast and dip steeply to the east throughout the district. These veins contain value in the form of argentiferous galena, sphalerite, and copper minerals. References indicate a total production of $1.2 million for all mines combined. Most of the mining properties in the district were patented in 1899 and are now under the control of Hyatt Ranches.

The Graphic mine, located in the geographic center of the district, was by far the most productive property in terms of value. Large prominent white dumps consisting of processed vein material can be seen from the main dirt road passing through the area. A few sphalerite crystals along with massive galena can be picked up on the dump. The main 650-ft shaft is caved to the surface. The Copper mine is located at the extreme northern end of the district. The property consists of several shafts, one reported to be 70 ft deep, and small pits. The mine has produced the following minerals of interest to collectors: wulfenite, vanadinite, mimetite, fornacite, mottramite, willemite, dioptase, murdochite, plancheite, creaseyite, bromargyrite, chlorargyrite, barite, quartz, and many chrysocolla pseudomorphs. The Rock Island mine property is located adjacent to the Copper mine on the south. The small dumps associated with several shallow shafts and pits have produced vanadinate and barite crystals. The Hub mine is located just north of the Graphic mine, and the dump around a caved shaft has produced descloizite and vanadinite crystals. The Keystone mine is located just south of the Graphic property and consists of a shaft with the remains of an old hand winze. The small amount of dump material available produced wulfenite, barite, mimetite, vanadinite, descloizite, mottramite, and galena crystals. At the far southern end of the district is located the Section 4 prospect. Here, the dump material from a pit consists of small vugs formed from vacated feldspar crystals in silicified andesite. The vugs contain small lustrous microcrystals of sphalerite, galena, quartz, barite, jarosite, and gypsum. The last property of consequence is the Jumbo mine located a short distance west of the Section 4 prospect. The property consists of one large open shaft and large white dump. Several small pits nearby produced dark-blue lathlike azurite crystals, barite blades, and cubic galena crystals.

Acknowledgments
Special thanks to Ron Gibbs for mineral specimen photography and for computerizing the presentation, to Bob Eveleth and staff at the New Mexico Bureau of Geology and Mineral Resources for access to the archives, to the volunteers at the Deming-Luna County Museum and staff at the Museum of New Mexico for helping to locate historical photographs, and to Leedrue Hyatt for permission to cross his ranchland.

References:

1. Couchman, D. H., 1990, Cooke's Peak???pasaron por aqui???a focus on United States history in southwestern New Mexico (cultural resources): Bureau of Land Management, Las Cruces District, Mimbres Resource Area, 268 pp.
2. Jicha, H. L., Jr., 1954, Geology and mineral deposits of Lake Valley quadrangle, Grant, Luna, and Sierra Counties, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Bulletin 37, reprinted 1980, 93 pp.
3. Lindgren, W., Graton, L. C., and Gordon, C. H., 1910, The ore deposits of New Mexico: U.S. Geological Survey, Professional Paper 68, 361 pp.