By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Socorro County, in the west-central part of the State along the Rio Grande, contains a variety of mineral deposits valued mainly for copper, lead, zinc, and, to a lesser extent, gold and silver. In 1921 Catron County was formed from part of Socorro County, and much of the early gold output attributed to Socorro County came from the Mogollon district now in Catron County. Total gold production through 1959, excluding the Mogollon district, was about 32,000 ounces, mostly from the Rosedale district. Though the Magdalena district is the most important camp in the county, its ores are rich in lead and zinc and have yielded less than 4,000 ounces of gold.
The Rosedale district is in the northern San Mateo Mountains in the southwest corner of So-corro County, about 25 miles southwest of Mag-dalena.
Gold was discovered in the district about 1882. Development work was delayed by frequent Indian attacks, but operations began in the 1890's and production was maintained until 1916 (Wells and Wootton, 1940, p. 19). The Rosedale mine, the most productive in the district, was active from 1934 through 1937. No detailed early production figures have been found, but Wells and Wootton (1940, p. 19) reported that the district produced about $500,000 (24,190 ounces) in gold through 1916. There was no placer production. No production was recorded from 1941 through 1959. The total gold production of the district through 1959 was about 27,750 ounces.
The San Mateo Mountains consist of rhyolite, tuffs and breccias (Gordon, in Lindgren and others, 1910, p. 259-260). The veins are in well-defined mineralized shear zones in rhyolite and rhyolite porphyry. Most of the ore is oxidized and consists of free-milling gold in a gangue of bluish-white quartz and small amounts of iron and manganese oxides. Sulfides appear below water level at a depth of about 725 feet. The higher grade ore is said to be associated with manganese oxide (Lasky, 1932, p. 95).
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