Page 80 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

MINING DISTRICTS 79
small but unlisted amounts from other properties. These mines may have produced ore worth $60,000, which would include all small-lot shipments from the outlying prospects.
BLACK MOUNTAIN GROUP
The Black Mountain (Minnehaha) group of three claims was located in 1881, and is reported to have yielded a small amount of rich ore from a small ore shoot shortly after its dis- covery. In 1931, Silver City, N. Mex., people acquired the prop- erty, and after driving a short tunnel on a cross vein (the Bullion vein) and sinking a winze on it to a depth of 200 feet, from the bottom of which short drifts were run, the property was closed down. No shipments were made during this period. The min- eralization consisted of irregular stringers of quartz traversing the fractured zone of the vein, and when the ore was hand sorted it assayed $30 per ton, principally in gold. The main north-south vein, locally called the Minnehaha, was not cut, but drifting along the Bullion cross break for about 200 feet would have encoun- tered it. The old workings on this main vein are said to be caved. The camp is equipped with blacksmith and carpenter shops, a portable compressor, hoist, and bunk and cook houses. It is re- ported that the owners of this group also bought the Great Re- public mine which adjoins the Black Mountain on the same vein system to the south.
GREAT REPUBLIC MINE
The Great Republic mine has been developed to the 400-foot level, but when visited all surface and underground workings were caved and inaccessible. The last work was done in 1923, when a 40-ton capacity tabling and flotation mill was erected. Sulfides were encountered at the 100-foot level, but above this, rich pockets of silver chloride were mined, and it is said that the finest specimens from the district came from a small pocket called the Jewelry Shop on the 175-foot level. A flat fault is said to cut the vein off below the 300-foot level, and it was not found on the 400-foot level. The ore occurs as stringers of quartz with pyrite, gold and silver, in a fractured zone of andesite breccia which has been much propylitized and impregnated with pyrite. It is said that the ore occurs in shoots within the vein, which is 2 to 10 feet wide, and that the mine contains 4,000 tons of this ma- terial blocked out, which assays $14 per ton. South of the mine about 1,200 feet, a northeast-striking fault has cut off the vein, and the southern portion of it has been moved 300 feet or more to the east. The northern segment of the vein ends against a block of Magdalena limestone. The vein appears to split be- tween the Republic shaft and this fault, and it is said that the hanging-wall fracture carried mostly silver, while the footwall fracture was richer in gold. It is believed, however, that the footwall fracture carries a later mineralization than the other, which is associated with the period of the rhyolite extrusion.