New Mexico Mineral Symposium — Abstracts

The Pine Canyon fluorspar deposit is in the Burro Mountains about 16 mi southwest of Silver City, Grant County, New Mexico. Claims on this deposit were first located in the early 1940s, although no ore was ever shipped (Gillerman, 1952). The deposit is currently under claim as the "Judith Lynn" and was located in April 1983. Thoughts of a significant fluorite recovery effort from the Pine Canyon deposit have intrigued us for the last ten years.

Fluorite from the Pine Canyon deposit has fascinated collectors since the 1970s when it first appeared on the mineral specimen market erroneously labeled as originating from Catron County, New Mexico. This bit of misinformation was corrected in an article by North and DeMark in the New Mexico issue of the Mineralogical Record (v. 20, no. 1, 1989). Digging with hand tools on the claim over the years had about reached an end as the trenches dug on nearly vertical veins became too deep to work effectively. We decided that the time had come for a mechanized fluorite dig.

Mike New of Top-Gem Minerals (Tucson, AZ) was contacted at the Denver Show in September 1993 about suggestions for equipment. He recommended the use of a tracked, 40-ton Caterpillar 320L excavator, which had been used very successfully at Morenci, Arizona to collect azurite and malachite. An agreement was reached between ourselves and Mike New and Joe Kielbaso of Top-Gem Minerals to commence the operation with the excavator on the 1st day of July, 1994. The operation was scheduled for two-weeks duration pending approval of the U.S. Forest Service as the mining claim was located within the Gila National Forest. Prior to operations commencing, however, the Forest Service required a detailed Notice of Intent that described the proposed mining plan, an archaeological survey, and clearance. In a good example of cooperation between the U.S. Forest Service and claim owners, Forest Service personnel (Mr. Robert Schloss) volunteered to accomplish the archaeological survey so that we could meet our start-up date of 1 July. A Notice of Intent was submitted to the Forest Service in mid-June that described in detail the scope of the digging to be accomplished. The Notice included the possibility that some drilling and blasting might be needed. We also advised that we would backfill all excavation and restore the surface topography to the degree possible to its original configuration. With all of the necessary steps completed, the Forest Service authorized us to proceed with the dig.

It was determined that most of the fluorite occurred in three primary veins that had a northeast-southwest strike and dipped about 70° northwest. Veins would pinch and swell along strike and dip with maximum width of about 20 cm. The host rock at the surface is an eroded Precambrian granite, and the fluorite mineralization is generally considered to be Tertiary (Gillerman, 1952). The working area for the excavation was roughly a north-south rectangle about 75 m long and 50 m wide. Fluorite crystals were found as fracture fillings lining granite walls and, between clay seams in the veins, usually in plates.

The mining plan was to dig as deep as possible parallel to the veins and as close to the vein as practicable with the machine. Next, the vein material would be extracted using hand tools. Vein material was then collected in buckets (between 6 and 15 buckets) that were transported to the washing area at the end of each day. The heavy clay and organic material enclosing the fluorite made it impossible to evaluate the specimens without some cleaning. A windmill and stock tank in Pine Canyon directly below the mining area was a ready source of water and proved to be invaluable to the cleaning and sorting effort. The buckets of vein material were soaked overnight, and the following day clay/fluorite chunks were broken apart and scrubbed with brushes so that the fluorite could be evaluated. Specimens were then graded in three categories: A (high quality), B (medium grade), and "54s" (student/beginner specimens).

In general, the two most southerly (upslope) veins produced the curved, scallop-faced, purple octahedrons most often associated with the Pine Canyon fluorite. The most northerly (downslope) vein produced fluorite that was markedly different. The octahedrons were much smaller but were very sharp and often associated with light green cubes less than 1 cm. Virtually all of the fluorite from both areas was coated with a druse layer of quartz up to 1 mm thick. On the last day of excavating, a small section of the center vein produced some unusually sharp octahedrons that, upon cleaning, proved to have exceptional clarity. Some of the crystals also had a more prominent zone of green in the interior. These were the only crystals found that were suitable for faceting.

The maximum depth to which the excavator could break rock and remove material was 2.5-3 m. To reach deeper on the veins, drilling and blasting were used. Mark Kielbaso, our expert excavator operator, was also our premier driller and blaster. A series of 8 to 11 holes 3-ft-deep were drilled parallel to the veins. These were loaded with ANFO (ammonium nitrate-fuel oil) "bombs" (two 15-cm charges) and a Kinepac "trigger" and were set off simultaneously using det cord and a fuse and cap. This method allowed us to reach a maximum depth of about 4 m on the veins.

We commenced reclamation of the area in the afternoon of the 14th of July. All trenches were filled, and the slope was contoured to its original configuration. A U.S. Forest Service agent (Bob Schloss) inspected the area that afternoon and proclaimed that the reclamation effort was satisfactory. That evening, the specimens were divided according to our pre-arranged contract, and the packing of specimens for transport began. Everything but breaking camp was complete. All agreed that the dig was a great success. No one had been hurt, the equipment worked perfectly, we all got along well, and most importantly, a large number and volume of superb fluorite specimens had been recovered. It doesn't get better than that!
 

References:

1. Gillerman, Elliot, 1952, Fluorspar deposits of Burro Mountains and vicinity, New Mexico: U.S. Geological Survey, Bulletin 973-F.