Page 114 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

MINING DISTRICTS 113
lead-copper ore, 750 tons of zinc concentrate, 420 tons of silver- lead concentrate, and 300 tons of lead concentrate.
It is reported that the ore at the Royal John mine occurs in a lens in limestone and that the chief metals are lead and zinc, with subordinate amounts of copper, silver and gold. A consid- erable tonnage of ore of moderate grade is said to be blocked out.
SIERRA CUCHILLO
CUCHILLO NEGRO DISTRICT
LOCATION AND GEOGRAPHY
The Sierra Cuchillo is located in the northwestern part of Sierra County. It is east of Fairview and extends from the northern border of the county in a southerly direction for 15 miles, where the Rio Cuchillo has cut through it in an easterly direction. (See Plate I.) South of this drainage line a series of low hills extends the range for 12 miles or more in a southerly direction. About 6 miles south of the Rio Cuchillo the Palomas River has cut transversely through these low hills, and at their southern termination the Arroyo Seco makes a wide sweep around them through the Tertiary and Quaternary detrital de- posits. Cuchillo Peak, the highest point in the range, has an ele- vation of auout 7,500 feet and is a short distance south of the hot Springs-Fairview highway, which crosses the range. On the higher le‘eis scrub oak and cedar abound. Yellow pines flour- ished on the northern slopes at one time, but most of these were cut down and utilized during the active days of mining. Three large ranches have headquarters in or sear the Sierra Cuchillo.
GEOLOGY
Commencing at the base of the westward-facing fault scarp of the Sierra Cuchillo, where the rock exposures emerge above the alluvial fans of the interior bolson plain in which Fairview is located, is a poor exposure of limestone about 50 feet thick. This has been doubtfully classed by the writer as Lake Valley (Mississippian). The rock is a light-colored massive to slabby limestone, in which no fossils were observed, nor could the normal unconformity that exists between the Lake Valley and Magdalena strata'be recogniZed. Overlying this bed is a considerable thickness of the Magdalena (Pennsylvanian) limestone. Immediately above the Lake Valley ( ?) limestone is a bed of dark brown to gray quartzite 100 feet thick, then 18 feet of shaly beds, and then 11 feet of dark brown quartzite. It is believed that these beds are a part of the Sandia (Lower Magdalena) formation recognized farther north in the State. From this point to the top of the ridge the beds are typical of the Magdalena limestone and are 1,070 feet thick in the section measured. They consist of hard massively bedded limestone with a few thin shale partings and