Mohave County miner and our mineral wealth., 1921-09-23
GENERAL GEOLOGY OF
 CATORCE MING DIST.
By Charles Laurence Baker,
 Berkeley, Cal.

bcIhSleH; NIl.
 The district of Catorce, San Luis Potosi, ranks among the first half dozen silver producing camps of Mex ico. Mining has been more or less continuous there for the last 15O years The large producing mines, Mapimi, Mazapil, Palomas, Musquiz, Minas Virjas, now for the most part idle or abandoned, are grouped around the head of two valleys; one which drains to the west, falls 2000 fit. in Az mi. between the main Catorce and the western foot of the range and is characterized by steep canon walls; the other, east of the main town of Catorce from which it is separated by high divide, heads in a number of steep tributaries above the basin in which lies the town of Potrero, and flows nearly north for 10 mi. to the northern base of the range; below Potrero, it has for the most part gently sloping valley walls and a broad valley floor.
 The Sierra Catorce is the highest range of the region, the summits reaching attitudes of over 11,OOO it. With the exception of few cliffs of the erosion escarpment of the lower limestone and the canon walls below the main town of Catorce, which is the highest town in Mexico, the gently rounded slopes are characteristic of maturely eroded mountain range composed of folded sedimentary rocks As is usual in desert regions, the heavy -bedded limestones are the most resistant to erosive forces. Folded into. anticlines, they form the noun tain ranges; and the intermontane valleys and basins, originally carved out of less resistant shades, clays, marls, and sandstones, are covered by debris forming a mantle with surface gradually rising upwards towards the hills. In time, the debris buries, in deposits formed from their own ruins, all but the highest summits of the original mountains; some of this region has already nearly reached this stage. Most of the debris is firmly cemented by calcium carbonate (caliche). Solution of the limestones by meteoric waters afforded the sup ply of lime'carbonate, which has been redeposited upon evaporation of the waters as cement binding the bould- CTS, pebbles, and finer detritus.
 In vegetation, topography, and pre- vailing hues of the desert landscape, the Catorce region greatly resembles parts of Nevada and the Mohave Desert.
 Metamorphic rocks are exposed in the canon from the main town of Ca torce westward to near the canon's mouth. These are divided into two series, and the relationship between the two is not known. The probably older series outcrops between the Pur- isima tunnel and the main town of Catorce. A less metamorphosed series probably forms a steeply dip ping anticline with axis in the vicin- " Ol Ille lOWel IOWH Ol CdIOICc anu outcrops between the Pursima tunnel and the exposure of the unmetamor- phosed sedimentaries near the mouth of the canon. The age of the meta morphics is not known; they might In part be as old as pre-Cambrian or as young as Jurassic.
 Unmetamorphosed d m e n tary rocks overlie the metamorphic rocks with strong angular unconformity. All the more productive ore deposits appear to be in the heavy-bedded limestone of these rocks, which Is 900 to 1000 fit. thick.
 In general, the upper sedimentary world war. Drew was killed in aerial combat. The song was written by