Page 181 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

178 GEOLOGY AND ORE DEPOSITS OF SIERRA CO., N. M.
ore was deposited along fractures extending a short distance into the Blue limestone, and in a few places it occurs in fractures in the roof of Crinoidal limestone, but these deposits have little commercial value. Where the chert has been fractured the ore is siliceous as a rule, but where the chert was undisturbed the solutions filtered through the overlying bed of limestone and re- placed it to form the basic ores of the district, in which the lime content is about 35 per cent and silica about 20 per cent. The solutions penetrating the fractured limestones first filled the frac- tures and spaces with a mixture of manganese oxides, silver minerals, and calcite, and later they dissolved out the fragments of limestone, leaving a coarse boxwork of the original cementing material ; still later these openings were filled by ore and gangue minerals. Where the secondary ore-depositing solutions precipi- tated their mineral content in fractures in the chert the silica content is as much as 60 per cent, the remainder consisting of limonite, manganese oxides, calcite and silver minerals. In the intermediate ores, as in the Emporia and Thirty-stope workings, the lime content averaged about 30 per cent.
HISTORY AND PRODUCTION 56
The Lake Valley ore deposits were discovered by George W. Lufkin in August, 1878. News of the discovery soon spread, and a rush for the new camp was shortly under way. The mines were worked almost continuously until August, 1893. The best properties were absorbed within a short time by three companies, named from the groups of mines the Sierra Grande, Sierra Bella and the Sierra Apache. For several years during the later active history of the camp, operations were conducted under the man- agement of the Sierra Grande Co., and after mining in the dis- trict ceased, the other properties were acquired by the Sierra Grande Co. The entire mineralized area, except for a few scat- tered holdings, is owned by this company. In the early eighties the Bridal Chamber, one of the richest single bodies of silver ore ever found, made the Lake Valley district famous.
These ore bodies are in close proximity to the Santa Fe trail and the old lanes of travel along the Rio Grande, and are marked in many places by prominent outcrops of black manganiferous flint. It seems strange that they were not discovered by the Spaniards, who passed and repassed them for nearly 300 years. 57 No ore is being mined in the district at present. Occasion- ally in the recent past small shipments of silver ore or fluxing material have left the district, and since 1910 these have amounted to 46,261 tons divided as follows : Silver or silver-gold ores, 2,658 tons ; lead or lead-silver ores from the Emporia incline section of the district, 210 tons ; manganese ore high in manga-
56Clark, Ellis, op. cit., pp. 138 and 150.
Gordon, C. H., op. cit. (U. S. G. S. Prof. Paper 63), pp. 276-277, and 281-282.
57Clark, Ellis, op. cit., p. 138.