Page 173 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

170 GEOLOGY AND ORE DEPOSITS OF SIERRA CO., N. M.
produced near the Sternberg shaft.
In the limestone in the southern part of the district, ores
containing vanadium, molybdenum, lead and manganese have been mined from irregular replacement bodies. These ore bodies have been largely worked out, and although other small pockets may be discovered from time to time, there is no assurance that they can be profitably mined except under the stimulus of extra- ordinarily high metal prices. At the north end of the district, at the fault contact between the limestone and the andesite, a replacement deposit in the limestone contains gold in moderate amounts. The average ore shipped contained 12 per cent lead and about $8 per ton in gold. This deposit is of interest, and plans have been discussed to sink along the contact until the lime- stone under the andesite is encountered.
The gold in the placers of the district has come from the eroded parts of the gold lode deposits. The gold has accumulated in alluvial fans, the principal fan heading at the entrance to Copper Flat. Near the head of this fan the gold is coarse and well concentrated, but as distance is gained from the source, commercial values quickly confine themselves to runs of mod- erate width and length, with poor material between, and the gold rapidly diminishes in size until at a distance of 2 to 3 miles from the head of the fan, the particles are extremely small, and the quantity is definitely below commercial limits except in a few small areas.
Several attempts made in the past to mine the lode and placer deposits of the district have been unprofitable, largely due to one or more of the following causes : (1) A large plant has been erected before actual reserves of ore have been blocked out, and capital funds have been depleted before development started, or the excessive size of the plant has ruined any possibility of mining a small to moderate sized ore body with profit; (2) money has been spent for development at places offering small chances for ultimate success, while more favorable areas have not been explored ; (3) well-conducted campaigns of exploration have been stopped because the companies financing them were looking for larger ore bodies than are characteristic of the district ; and (4) sampling has been inadequate or has been neglected.
LAKE VALLEY HILLS
LAKE VALLEY DISTRICT
LOCATION AND AREA
The Lake Valley district has been described by Clark 49 and by Gordon, 50 who used much of Clark's material. In the present bulletin the writer has utilized considerable information given
49Clark, Ellis, The silver mines of Lake Valley, New Mexico: Am. Inst. Min. Eng. Trans
50Vol. 24, pp. 138-167, 1894.
Gordon, C. H., op. cit. (U. S. G. S. Prof. Paper 68), pp. 278-281.