New Mexico Mineral Symposium — Abstracts

Intensive mining for specimens and exploratory activity at the Blanchard mine in 1988 resulted in a number of unexpected, as well as expected, discoveries. Activity was widespread throughout the various tunnels, numerous prospects, and outcrops. In mid-June a backhoe was brought in with three specific goals in mind:

1) opening the Sunshine #6 tunnel that had been blasted/bulldozed shut;

2) exploratory trenching in the Clarence Barrett workings;

3) developing the working area in the vicinity of the ore bin in the Portales/Glory Hole area.

The Sunshine #6 tunnel was closed in 1979 by the operators (Western General Resources) because of hazardous conditions inside the tunnel. Specimens from this particular tunnel were mainly responsible for establishing the reputation of the Blanchard mine as a producer of rare and beautiful minerals. Sprays of delicate brochantite needles, druses of linarite on thin barite blades, and very fine spangolite specimens were all products of this tunnel. Additionally, superb specimens of aurichalcite, murdochite, and platternite were found in this prolific tunnel.

The reopening of the #6 tunnel was accomplished relatively easily. Upon entry, it was obvious that considerable deterioration of the ceiling, walls, and pillars had occurred, and safety was a paramount concern. Several large sections of the ceiling had collapsed onto the floor, and near one of the central pillars, several large boulders had dropped, splintering an 8" x 8" support timber. Most disappointingly, the area that had produced the exceptional spangolite specimens was covered by at least 20 ft of debris deposited when the opening had been bulldozed shut. After minor exploration, the tunnel opening was closed once again.

Exploratory trenching in the Clarence Barrett prospect area revealed extensive cave-type formations in one spot with numerous large selenite crystals as long as 45 cm and sporadic blue fluorite crystals. Farther south, large plates of fluorite-coated rocks were pulled from an outcrop. Fluorite from this location is a lustrous blue with a purple tint, and individual crystals are commonly 2.5 cm on an edge. The final area for backhoe operations was the outcrop exposed in the trench across from the Portales-era ore bin. For several years this area has produced good-quality blue fluorite cubes about 1-2 cm on an edge. Additional quantities of excellent blue fluorite were recovered from this area. More surprising was the discovery of large numbers of bipyramidal wulfenite crystals coating many of the more lustrous fluorite cubes. These wulfenite crystals are about 1 mm in length, and with their bright luster and orange color they contrast vividly with the blue fluorite.

Sphalerite, the primary sulfide mineral, has always been scarce at the Blanchard mine. The only significant occurrence of in-situ sphalerite has been the Sunshine #4 tunnel where it is found in massive gypsum and often coated with a crust of pyrite crystals and, occasionally, covellite crystals. This past year, the tunnel has been the discovery site of several minerals that had not been reported previously from the Blanchard mine. A 2-m-long seam in the floor at the southern end of the tunnel has produced highly lustrous rosettes and clusters of hemimorphite crystals with an unusual reddish-brown color.' The crystal groups, some of which are stalagtitic, occur in vugs and pockets as large as 0.5 m across. Close examination of these specimens revealed seams and blebs of massive cuprite intergrown with solid masses of cerussite, hemimorphite, and in one case a 2-cm linarite crystal. In many cases, the cuprite is included within the hemimorphite as very fine veils and zones (Hlava, pers. comm. April 1988) accounting for the unusual color. Native copper also has been found in a couple of instances as very minor hackly masses imbedded in the cuprite. Aurichalcite sprays and rosasite balls often accompany the hemimorphite crystal groups, and in one section, groups of 1-2-mm sea-green smithsonite crystals were recovered. Cerussite crystals, some in V-twins more than 1 cm long, were found in an area adjacent to and below the hemimorphite zone. The post-mining minerals, chalcanthite and goslarite (Hlava, pers. comm. April 1988), have also been found within and coating massive gypsum at the southern end of the tunnel.

A short west-trending drift near the tunnel entrance has produced a most startling find this-past year. Malachite pseudomorphs after linarite crystals more than 3 cm long have been recovered. In most crystals replacement has been complete, but in some cases a solid core of linarite remains. The crystals are found singly and in radiating groups in 5-20-cm-wide vugs in very tough silicified limestone. Unfortunately, most crystals are detached from the matrix in opening the pockets. The vugs also contain 1-3-mm-long hemimorphite crystals, usually pseudomorphed by chrysocolla, small tufts of malachite, and a white clay-like mineral coating the drusy quartz crystals that usually line the pockets. No unaltered linarite crystals have been recovered to date, but the search continues.

Perhaps the most unexpected new mineral occurrence at the Blanchard mine this past year was that of a mercury sulfide identified (Hlava, pers. comm. April 1988) from locations near the Portales tunnel (Glory Hole). X-ray diffraction has confirmed this mineral to be cinnabar (Foord, pers. comm. Sept. 1988). The cinnabar occurs as orange-red, pulverulent coatings in small cavities or in roughly square patches in what appears to be relict casts of a completely decomposed mineral. The cinnabar occurs within a very restricted horizon of altered gypsum-bearing punky limestone roughly 10-12 cm thick. It occurs above a zone containing cavities lined with blue fluorite crystals. The cinnabar has been found in the same horizon at two points approximately 50 m apart.

Additional exploratory work at the Blanchard mine is planned for the coming year and very possibly could reveal new and exciting discoveries. The intrigue of minerals is in large part due to our pursuit of them.