×Figure 1. CPD collecting trip, May 2015. Left to Right: Ray Demark, Hugo Brown, Fred Ortega, Chris Cowan, Ames Austin, Phil Simmons.
The Cooke’s Peak district (CPD) and Jose mining districts are located on the northeast and northwest sides (respectively) of Cooke’s Peak, a prominent geographical feature in southwestern New Mexico (NM) about 18 miles north of Deming, NM.
Geology Cooke’s Peak is an early Tertiary (39 million year ago [MYA]) granodiorite stock intruded into much older (about 400 MYA) Silurian and Devonian Fusselman dolomite and Percha shale sediments. The main ore bodies in both districts typically occur as isolated pod-like replacement deposits in the Fusselman below the impermeable Percha shale “dam.” Ores consisted mainly of argentiferous galena, sphalerite, cerussite, minor smithsonite, with a gangue of fluorite, quartz, calcite and pyrite.
History Initial mining claims in the districts were located from about 1876–1880. The bulk of mining activity occurred from 1880 to 1905, and by 1905 the richest ore deposits were exhausted. Early mining activity ended by 1911, and the districts were dormant until a second brief period of mining took place during a revival in the CPD from 1951 to 1953. Total production from these relatively small mining districts since 1953 has been about $1 million in lead and zinc values to date. There has been no reported commercial mining activity in the districts since 1953.
Mineral Collecting Activities The primary focus of this talk will be mineral collecting adventures in the CPD, and also in the more obscure small Jose district. Although of no importance to the commercial miners, for mineral collectors fluorite is the mineral of choice to be found in the CPD. Very nice specimens of quartz epimorphs after calcite and vanadinite have also been recovered from a Jose district mine.
Those of us who have collected in this area have been fascinated by the fact that two very distinct varieties of fluorite can be found on individual specimens from the CPD. On individual specimens, fluorite occurs initially as blue-gray modified cubes to 2.5 centimeters that were then overgrown by dark purple octahedrons up to 7 centimeters on edge, with a core of bottle-green fluorite. The two generations of fluorite are always separated by a thin clay layer. These combination-type fluorite specimens are unique and immediately recognizable by those familiar with CPD material. Another recent significant discovery in the CPD consists of dark green octahedral fluorite specimens with individual crystals up to about 5 centimeters on edge. Very noteworthy large specimens of both the combination fluorite, and the recent dark green material from the CPD are on display in the new New Mexico Bureau of Geology and Mineral Resources mineral museum in Socorro, New Mexico.
The CPD and Jose districts are obscure small New Mexico mining districts about which very little has been published in the literature, and there is very little material from these localities available on the mineral specimen market. In addition, the New Mexico Mining and Minerals division (NMMD), Abandoned Mine Lands group in conjunction with the Federal Bureau of Land Management (BLM) are currently working to close the remaining accessible small workings in the CPD district, so recovery of specimens is somewhat of a race against time before closure activities are completed in this historic mining area.
Figure 2. CPD combination fluorite specimen, 7.5 by 5 cm, collected 1969.
