Mariposa County California Gold Production
MERCED RIVER PLACERS
MORMON BAR DISTRICT
The Mormon Bar district is in T. 5 S., R. 18 E., about 2V& miles south of the town of Mariposa.
In the early days of mining in Mariposa County, the headwaters of Mariposa Creek near Mormon Bar was the scene of considerable placer activity. By 1870, however, the deposits, which were only about 6 feet thick, were almost worked out, and thereafter the placer output of the entire county averaged only a few hundred ounces per year (Julihn and Horton, 1940, p. 159, 162). In the late 1930's a slight revival took place, and the gravels at Mormon Bar were worked industriously by dragline (Julihn and Horton, 1940, p. 159). Total gold production for the district is estimated at about 75,000 ounces.
MOTHER LODE AND EAST BELT DISTRICTS
The Mother Lode, which has its southern terminus in Mariposa County, is a northwest-trending zone that is 3 or 4 miles wide and extends from the town of Mormon Bar northward through Coulterville into Tuolumne County. Roughly parallel veins east of this zone are referred to as the East Belt.
Though much has been said about the production of the Mother Lode, the mines of the East Belt and West Belt (Hornitos) districts have produced most of the lode gold in Mariposa County. Recorded production from mines on the Mother Lode to about 1939 totaled $6,300,000 (Julihn and Horton, 1940, p. 103-116). Prominent among these are the Princeton, Pine Tree and Josephine, and the Mount Ophir. The East Belt in Mariposa County is a continuation of the same belt in Tuolumne and Calaveras Counties, to the north. Incomplete production data from individual mines give a minimum total of almost $12 million in gold to about 1939 (Julihn and Horton, 1940, p. 134-158). The major mines in this area are the Original and Ferguson, Hite, and Mariposa. Total gold production of the Mother Lode and East Belt districts through 1959 was approximately 1,009,000 ounces.
PLACERS IN TERTIARY GRAVELS
Placers in Tertiary gravels at three localities were reported by Bowen and Gray (1957, p. 189) to be gold bearing: in the Blanchard district in the northwestern part of the county; along the Tuolumne County line, just south of Jawbone Ridge; and on the ridge between Moore and Jordan Creeks, 4 or 5 miles northwest of Bower Cave.
The protective cap of Tertiary lavas that preserved the gravels in counties to the north probably did not extend as far south as Mariposa County; consequently, most of the Tertiary alluvial deposits have been eroded away. The remaining deposits yielded considerable gold in the early days, but their production is unrecorded. They probably produced a maximum of about 75,000 ounces of gold.