Page 168 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

166 GEOLOGY AND ORE DEPOSITS OF SIERRA CO., N. M.
cut in one of the crosscuts, where it is said to be 8 feet wide and much fractured and brecciated.
OTHER LODE MINES
Numerous other properties in the district, some with a rec- ord of production and others hardly beyond the small prospect stage, surround Copper Flat on the inside slope of the hills to the northwest, west and southwest. Among these is the Buetecke tunnel above the El Oro mine, which is 450 feet long. At the portal this tunnel cuts a wide dike reported to carry $3 to $4 gold, while farther in the hill it penetrates an irregularly frac- tured mass of andesite, in which metallization is weak and spotty.
The Tripp and Homestake mines are near the top of the ridge about a mile due west of the El Oro shaft. Each of these mines has been opened extensively by shafts, tunnels and open cuts, and the surface gives evidence that fairly large stopes were mined in the oxidized zone. The combined production of these mines is reported to be about $50,000. The writer did not enter either of these mines, due to the unsafe condition of the work- ings. It is understood that the El Oro Mines Co. owns both properties.
The Empire mine, in the next main draw northwest of the Mary Richmond mine, is on the north slope and near the top of Empire Peak. The production from this mine is given as $1,000. The workings, consisting of pits, tunnels and shafts, have pros- pected a fracture zone in the andesite that crosses the ridge at the head of one of the tributaries to Grayback Gulch.
ANIMAS (HILLSBORO) PLACERS
Aside from the small placer areas at the foot of Snake Gulch and in Wicks Gulch, both of which are probably almost ex- hausted, all of the promising placer ground in the Hillsboro district is east of the Animas Hills. These placers are part of an alluvial fan that consists of detrital rock resulting from the ero- sion of the Animas Hills and Copper Flat. At the present time this fan is being dissected by the drainages of Dutch, Grayback, Hunkidori and Greenhorn gulches.
The basal part of the original fan is composed of fine to coarse fragments of rhyolite derived from the late flows of that material that once covered the Animas Hills. The intermediate part of the fan is composed principally of andesite and latite fragments, and it contains varying amounts of placer gold throughout. The topmost portion of the fan, which is low in gold content, is composed of basalt, andesite and latite frag- ments. Between the period of deposition of the basal part of the fan and the intermediate part, a period of quiescence or equi- librium must have existed, for just above the basal portion there is a bed of caliche, known as a false bedrock, upon which a large amount of gold has been concentrated. This caliche was formed by the deposition of calcium carbonate from water that rose to