Bagby-Mariposa-Mount Bullion-Whitlock Mining District, Mariposa Co., California, USAi

Regional Level Types
Bagby-Mariposa-Mount Bullion-Whitlock Mining District	Mining District
Mariposa Co.	County
California	State
USA	Country

A Au-Ag-Cu-Pb-Sb-Ni-Co-As-gemstone mining area located near the southern end of the Motherlode Belt.

This district is comprised of several former smaller districts:

Bagby District:

Location: This district is in western Mariposa County in the vicinity of the towns of Bagby and Bear Valley. It is in the Mother Lode gold belt. History. The streams were placer-mined early in the gold rush, and the Pine Tree and Josephine veins were discovered in 1849. Part of the area was on the Las Mariposa Spanish land grant of General John C. Fremont. Bagby was first known as Benton Mills, named by Fremont for Senator Thomas Hart Benton, his father-in-law. It was renamed in the 1890s for A. Bagby, a hotel owner. The town was a stop on the Yosemite Valley Railroad, which once extended up the Merced River canyon to Yosemite National Park. Gold mining activitv' continued until around 1875. There was mining in the district again in the early 1900s. The Pine Tree-Josephine mine was worked on a major scale from 1933 to 1944, and the Red Bank mine has been active in recent years. Part of the area, including the old town of Bagby, was inundated by the Exchequer Reservoir in 1967.

Geology: In this district the Another Lode gold belt is .about 1 Yi miles wide. It is underlain by northwest-striking beds of slate, phyllite, and metasandstone of the Mariposa Formation (Upper Jurassic), with greenstone and green schist both to the west and southeast (see fig. 18, page 95). A belt of serpentine extends northwest through the central portion of the district and is structurally important in relation to some of the gold-bearing veins. Ore deposits. There are several northwest-trending vein systems that consist of quartz veins and stringers with brecciated slate, schist, and associated bodies of pritic ankerite and mariposite-quartz rock. These vein systems are often scores of feet in thickness. The ore contains free gold, pyrite, and arsenopyrite with small amounts of chalcopyrite, galena, millerite, sphalerite, and niccolite. Milling ore averaged 1/7 to 1/2 ounce of gold per ton. In places high-grade ore is abundant. The ore shoots had stoping lengths of up to 600 feet, and the veins were mined to an inclined depth of 1500 feet.

Mines: Dolman, French ($116,000), Jumper, Juniper, Live Oak, Mexican I ($50,000), Oso ($50,000), Pine Tree-Josephine ($4 million), Queen Specimen, Red Bank ($100,000), Specimen.

Mariposa District:

History: This district is in the vicinity of the town of Mariposa at the southeast end of the Mother Lode gold belt. The Mariposa mine was reported to have been discovered in 1849 by Kit Carson, and the first stamp mill in California was installed there that same year. Much of this district was part of the Las Mariposas Grant of General John C. Fremont. The old courthouse in Mariposa erected in 1854 is the oldest continuously used courthouse in California. The mines were worked until the early 1900s and again during the 1930s. The Mariposa mine has been prospected in recent years.

Geology and Ore Deposits: The district is underlain by northwest-trending belts of slate of the Mariposa Formation (Upper Jurassic), serpentine, and greenstone. There are several massive quartz veins in slate or greenstone. The ore contains free gold, pyrite, and arsenopyrite, which often is associated with highgrade ore. The Mariposa mine has been developed to an inclined depth of 1500 feet.

Mines: Evans II, Kane, Mariposa ($2,395,000),
Stockton Creek, Stockton Creek Tunnel.

Mount Bullion District:

Located in westcentral Mariposa County about seven miles northwest of Mariposa. The district is in the southern end of the Mother Lode gold belt and extends northwest towards Bagby and Bear Valley (fig. 18). It includes the Agua Fria and Mount Ophir areas.

History: This region was first placer-mined in 1848, many of the miners having been of Spanish descent. Agua Fria Creek and other streams were highly productive (Agua fria means cold water in Spanish). Lode gold-mining began shortly afterward. Much of this district is in the Las Mariposa land grant, which originally belonged to General John C. Fremont. The mines in this grant were not located and surveyed in the same fashion as those on public lands, and to this day the land plats within this grant are difficult to coordinate with established survey lines. The grant later underwent lengthy litigation, and Fremont eventually went bankrupt. He named nearby Mount Bullion for his father-in-law. Senator Thomas Hart Benton, who was sometimes known as "Old Bullion." At Mount Ophir, which is now a ghost town, are the ruins of an early-day mint. From 1849 until 1854 private coinage subject to federal inspection was authorized in California. It is believed that some of the now extremely rare and valuable octagonal fifty-dollar gold slugs were minted here from locally mined gold. Gold mining in the district continued fairly steadily from the 1850s through the 1870s. There was considerable activity from around 1900 to 1920 when the Princeton and other mines were worked. Some mining was done in the 1930s and early 1940s, and there have been a few intermittent small-scale operations since.

Geology: As shown in figure 18, the gold mineralization is confined chiefly to a northwest-trending belt of slate, phyllite, and metasandstone of the Mariposa Formation (Upper Jurassic). Within this formation are two belts of pyrite-bearing metarhyolite that may have possible future economic significance. Greenstone of the Pefion Blanco Formation (Upper Jurassic) crops out to the east and west. Also present are thin bands of serpentine and numerous aplite dikes.

Ore Deposits: Several north-northwest-striking systems of quartz veins occur principally in slate. The veins usually range from four to 10 feet in thickness, although there are some massive ones that are considerably thicker. The ore contains free gold and pyrite, which is abundant in places. Millng ore yielded from ¼ to ½ ounce of gold per ton, and considerable highgrade ore was recovered close to the surface. Some of the ore shoots were extensive; several in the Princeton mine had stoping lengths of more than 500 feet. The greatest depth of development is 1,600 feet on the incline. A number of extensive vein systems have not been thoroughly explored. Also, there are several extensive 1970 deposits of pyritic metarhyolite in the Mariposa Formation that in places contain gold. These bodies are several miles long and 60 or more feet thick.

Mines: Greens Gulch ($119,000+), King Midas, Louis, Mt. Ophir ($250,000 to $300,000), Mountain View I, Nellie Kahoe, Ortega, Princeton 1 $ 5 million), Sorrel.

Whitlock District:

Location: The Whitlock district is in west-central Mariposa County five miles north of the town of Mariposa. The district is east of the Mother Lode gold belt and includes the Colorado, Sherlock Creek, and Whiskey Flat areas. The area was placer-mined soon after the beginning of the gold rush, and lode mining began shortly afterward. A number of mines were active here during the 1930s, and a few, such as the Diltz and Schroeder mines, have been intermittently prospected in recent years.

Geology: Greenstone and green schist underlie much of the district, with some slate, phyllite, and mica schist in the north portion. Granitic intrusives and serpentine are to the south. There is an appreciable number of diorite, quartz-diorite, and aplite dikes that commonly are associated with the gold-quartz veins. A northwest-trending fault extends along the west side of the district (see fig. 18).

Ore Deposits: Numerous north- and northweststriking quartz veins contain small but rich ore shoots. The veins usually are one to five feet thick, and a number dip at low angles. The veins have a tendency to roll or bend, and it is in these bends or rolls that the high-grade pockets often occur. Much specimen ore has been produced in the district; in 1932 the Diltz mine yielded 52- and 40-pound masses of gold and quartz. The greatest depth of development is about 900 feet.

Mines: Buffalo, Champion, Colorado ($50,000), Diltz ($750,000 to $1 million), Geary, Golden Key ($154,000), King Solomon, Landrum, Nutmeg ($180,000+), Our Chance, Permit, Schroeder ($200,000 to $300,000), Spread Eagle ($425,000), and the Whitlock ($500,000).

References

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