Page 106 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

MINING DISTRICTS 105
foot level, 4 feet of ore has been exposed that will assay 60 ounces of silver and $2.50 in gold to the ton. No tonnage of this mate- rial appears to have been blocked out.
FUTURE POSSIBILITIES
Water is a problem in all of the mines of the district below a very moderate depth, and it is said that for this reason the mines were restricted to operations on the upper levels. In the few places that the writer was able to visit underground, how- ever, he noted distinct evidence of the dying out of secondary en- richment and oxidation features, even above water level, and it is quite probable that, except for a relatively few small shoots of high-grade primary ore that may extend to some depth, the metal content in general below water level is very close to, if not actu- ally below, an economic limit for this district. (See footnote, page 59.)
A significant fact in regard to past production is that even while high prices prevailed during the World War, only a moderate amount of ore was shipped from this district, princi- pally from the Lady Franklin mine. No doubt other shoots of ore will be found from time to time, many of which have no out- crop on surface, but no scheme of development in this district is indicated except to follow stringers from known bodies in the hope that others will be encountered.
Among the mine operators and geologists who are familiar with the Kingston district are some who are impressed with the possibility of large ore deposits at depths greater than have been reached by past development work. The theory upon which these premises are based appears to be that nearer the intrusions and at greater depths, where higher temperatures and pressures pre- vailed, contact metamorphism of the limestones would be more pronounced, and large contact deposits of zinc-lead ore might have formed. However, the pre-Cambrian rocks are not far from the surface in the district, and it is doubtful if conditions were conducive to extensive contact-metamorphism above this unfav- orable host rock. Furthermore, the original lead-silver solutions of the known productive area were certainly weak, and the value of the ores formed by them was dependent largely on secondary processes. It is difficult for the writer to see, therefore, how these solutions could have formed rich primary ore deposits of another type at such a short distance below the present known ore horizon.
TIERRA BLANCA (BROMIDE NO. 1) DISTRICT
The writer spent two days in the Tierra Blanca district, one of which was at the Lookout mine and its immediate vicinity. Much of the information contained in the following sections has been extracted from Gordon's report, 42 with which has been
incorporated verbal information supplied by D. M. Miller of Lake
42Gordon, C. H., op. cit. (U. S. G. S. Prof. Paper 68), p. 271.