Page 125 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

124 GEOLOGY AND ORE DEPOSITS OF SIERRA CO., N. M.
Over large areas the cracks and fractures have been coated with a bluish-white film of chalcedony, and in many of the more open fractures specular hematite and cassiterite have been deposited in a manner quite similar to that of the Taylor Creek tin district. (See pages 69 and 70.) Along the dry washes which lead out of the range and over the gravel deposits, placer tin is found in rounded grains and nuggets that vary in size from one inch or more in diameter down to particles of 80-mesh size. Since the writer's visit to the district late in 1931, T. C. Parker63 has found an area in which he believes the metal may be present in impor- tant amounts. No tin has been produced commercially in this area.
OTHER DEPOSITS
South of the Dictator ground is an old group of three pat- ented claims, two of which are adjacent and the third at some dis- tance from these two, but all located on the contact, which here consists of monzonite porphyry intrusive into andesite breccia. So far as known, no shipments have been made from these claims, and only surface prospect holes have been sunk, but in nearly all of them there are showings of oxidized lead-zinc-copper ore. It is believed that the limestone and monzonite contact is but a short distance below the surface on these claims, and the evidence points to a continuation of the ore-bearing zone of the Dictator ground southward into this property.
FUTURE POSSIBILITIES
On the west side of the Sierra Cuchillo in the Rifle Shot and Confidence groups, and on the east slope in the Black Knife and claims to the north, the ore follows fractures in the tops of the slight arches in the limestone. These arches trend northeast and their axes pitch 25° in the same direction. As far down the pitch as the workings extend, the ore consists of sulfide and oxi- dized minerals of copper, lead and zinc, and some enrichment has probably accompanied the oxidation. What the grade of unal- tered primary ore is and how far down the pitch of the arches it continues must be determined by future development. It would seem, however, that exploration should be limited to following the stringers of ore found at or near the surface, and working them until the cost of development and mining exceeds the net profit from these operations. Extensive prospecting is probably not warranted in this part of the district, but a few shallow pros- pect holes in the silicified limestone along the crests of arches overlying the monzonite sill and in the silicified zone that trends northwesterly from the Covington claims, would give desirable information.
In the Dictator and Covington claims and along the contact to the south, however, a different type of exploration is war-
63 Written communication.