Page 186 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

MINING DISTRICTS 183 stated by Clark that a wagon-load of ore from a pocket in this ground yielded $20,000. The Last Chance workings are scat- tered; two shafts with stopes are located north of the Bella Shoot, one of these being at the contact along the Columbia fault, and the third stope is south of the Bella stope. Manganese ore was found along the contact at a depth of 14 feet. The ore body was opened up in its richest part, where the ore was basic. In the shaft considerable cerargyrite and large percentages of iron and manganese were present in the ore, with little silica. At a dis- tance of 50 feet from the shaft, however, it is reported that the content of silver, iron and manganese had decreased and silica had increased, so that the ore was no longer salable as a basic flux. At 87 feet from the shaft silver was so low and the silica
so high that the ore was no longer profitable to mine.
In all the Bella workings, but little folding of the beds is noted, aside from the gentle dip and warpings characteristic of
all the beds in this tilted fault block. As a con,equenc,3 of this lack of distortion the iron- manganese- chert layer is but little
fractured, and the rich secondary ore has replaced the Crinoidal beds immediately overlying the chert. Some ore occurs in the Blue limestone in this area, but it is where the Crinoidal beds are absent, or because of some purely local features. Minor fracturing of the beds occurred after the introduction of the chert layer and before the deposits were enriched by secondary processes. This is clearly evident in many of the stopes where rich secondary ore ends abruptly against such fractures, while the primary chert layer, which has been displaced a few feet, continues beyond the fracture with only minor enrichment or none at all.
APACHE WORKINGS
Northeast of the Columbia fault considerable work was done
along the contact of the Crinoidal and Blue limestones in open cuts and through shallow shafts in what are now called the Apache workings. The ore was close to the surface and under a thin shell of a hanging wall. The production was principally iron- bearing fluxing material, the silver content in general being very low. The workings expose a considerable tonnage of siliceous iron-bearing material containing but a few ounces of silver per ton. Clark notes that on the Bacon claim of the Apache group much money was expended in prospecting the ground, much of which contained abundant iron-flint, but with the exception of float taken from the surface no ore was ever shipped.
FUTURE POSSIBILITIES
Prospecting in the Lake Valley district near the contact of the Blue and Crinoidal limestones should result in the discovery of small pockets and stringers of high-grade silver-bearing ores. With higher prices for silver than have existed for the past four years, quantities of ore may be won from old stope pillars and