By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Mohave County, in the northwestern corner of Arizona, ranks second among the gold-producing counties of the State, with a total of about 2,461,000 ounces through 1959.
More than half of this total came from lode mines of the San Francisco district. Three other districts have produced more than 10,000 ounces: Wallapai, Weaver, and Gold Basin. All these districts are in the west-central part of the county, an area of mountain ranges and valleys that trend north-northwest.
GOLD BASIN DISTRICT
The Gold Basin (Salt Springs) district is in the eastern part of the White Hills west of Hualpai Wash, 40 miles north of Hackberry and 60 miles north of Kingman.
Gold-bearing veins were discovered in the early 1870's, but their development was inhibited by the remoteness of the area and scarcity of fuel and water (Schrader, 1909, p. 118-127). Before 1900, however, the district yielded gold ore worth between $50,000 and $100,000, most of which came from the Eldorado mine.
Production continued to 1920 on a small scale and a period of inactivity from 1920 to 1932 followed. A few mines were reopened from 1932 to 1942, but the district was dormant from 1943 to 1959. Total minimum gold production of the district was about 15,000 ounces, most of which was from lode mines.
The ore deposits occur in veins in Precambrian granite and schist. The gold is associated with lead or copper ores that contain pyrite, chalcopyrite, galena, molybdenite, and wolframite. The oxidized parts of the veins contain limonite, malachite, cerussite, and vanadinite (Schrader, 1909, p. 119).
SAN FRANCISCO DISTRICT
The San Francisco district is near the south end of the Black Mountains about 29 miles by road southwest of Kingman. It includes both the Oatman and the Katherine camps; Gold Road and Union Pass are local names applied to parts of the district. Gold is the principal valuable metal in the ore deposits of this district.
Soldiers from Camp Mohave on the Colorado River first discovered gold in the Oatman area in 1863 or 1864, in what is now known as the Moss vein (Ransome, 1923, p. 3-8). Other veins with prominent outcrops were discovered soon afterward. Although some rich ore was taken from a pocket close to the surface in the Moss vein in the first 3 or 4 years, most of the development was discouraging and the Oatman camp was inactive for more than 30 years.
The earliest locations in the Katherine area were probably made in the early 1880's (Lausen, 1931, p. 13). In 1901 good ore was found in shallow shafts on what is now known as the Tom Reed vein, and in 1902 a stampede to the district occurred when rich ore was found in the outcrops of the Gold Road vein (Ransome, 1923, p. 4; Schrader, 1909, p. 153-154). A high level of activity continued through 1924.
The district was revived from 1930 through 1942, and produced a maximum of 48,000 ounces in 1936. From 1943 through 1951, activity was sporadic and was carried out on a small scale, and from 1952 through 1959 no production was reported. The total gold production of the district from 1897 through 1951 was about 2,045,400 ounces.
In general the geology of the district can be described as an uneven terrain of Precambrian rocks overlain unconformably by a thick section of Tertiary volcanic rocks including trachyte, andesite, latite, rhyolite, and basalt flows. The volcanic rocks are the predominant bedrock in the Oatman area, whereas the Precambrian granitic rocks crop out extensively in the Katherine area (Lausen, 1931, p. 22-23).
Bodies of quartz monzonite porphyry, sodic granite porphyry, and rhyolite porphyry intruded Precambrian and the lower Tertiary rocks. The rocks were tilted and faulted, and mineral deposits were emplaced in the fractures in late Tertiary time. Most of the deposits are in the Oatman Andesite, although in the Katherine area important deposits are found in faults in the Precambrian granite (Lausen, 1931, p. 101-124).
The veinfilling is a typical epithermal mineral assemblage. Bands of quartz, calcite, and adularia contain clusters and stringers of native gold, hematite, limonite, manganese oxides, fluorite, and a little pyrite, chalcopyrite, and chrysocolla (Lausen, 1931, p. 58-62).
Located near the center of the Cerbat Mountains, which extend north-northwestward from Kingman for about 30 miles, the Wallapai district includes the mining camps of Chloride, Mineral Park, Cerbat, and Stockton.
Unlike the San Francisco district immediately to the southwest in the Black Mountains, where gold is the principal metal, in the Wallapai district lead-zinc ores are prevalent and silver and gold are chiefly byproducts. Many of the veins in the Cerbat Mountains were discovered in the early 1860's by prospectors in search of precious metals (Schrader, 1909, p. 51, 80, 91, 107).
Chloride, founded in the early 1870's and named from the character of its rich silver ore, was the first settlement in this area. Ores rich in gold and silver yielded a large production in the 1870's, but activity waned when the price of silver began to decline in 1882. Base-metal ores below the oxidized zone apparently were not mined extensively until the completion of the branch railroad from Kingman to Chloride in 1899 (Nolan, in Hewett and others, 1936, p. 19). Thereafter leadsilver ores were mined, and subsequent improvement in milling methods led to exploitation of complex lead-zinc ores (R. M. Hernon, in Arizona Bur. Mines, 1938, p. 111).
Zinc-lead mining reached its peak from 1915 through 1917 owing to high metal prices during World War I, declined abruptly after 1917, and thereafter exploitation was confined to veins with a relatively high gold content. Gold production began to increase in 1935 and reached its peak in 1937-38 (Dings, 1951, p. 126). After 1942, activity declined sharply, and from 1950 through 1956 gold production was less than 100 ounces annually. None was recorded for 1957-59.
From 1904 through 1956 the mines of the district produced 125,063 ounces of gold. Dings (1951, p. 125) estimated the value of combined metals produced before 1904 at $5 million, but the amount of gold represented in this total is unknown.
The rocks of the district consist of granite, gneiss, and schist of Precambrian age, stocks and irregular bodies of granite and gabbro probably Mesozoic in age, and still younger dikes of lamprophyre, rhyolite, granite pegmatites, and porphyritic granite. The veins, which occur in all rock types, occupy fault fissures; a few follow dikes (Dings, 1951, p. 127-139).
The veins that yield most of the gold consist mainly of fine-grained quartz with pyrite, sphalerite, galena, and chalcopyrite. The veins locally include arsenopyrite, proustite, molybdenite, and argentite and rarely include tennantite, pearceite, and polybasite. Other gangue minerals are calcite, manganiferous siderite, and rarely rhodochrosite. Gold and silver are in the galena and sphalerite.
The sulfides have been moderately oxidized to depths of about 75 to 200 feet, and partly oxidized ore has been found down to 600 feet. The principal ore minerals in the oxidized zone are cerargyrite, native silver, cerussite, and native gold, and the most common gangue minerals are limonite and limonitic quartz (Dings, 1951, p. 141-142).
The Weaver district is in the northern Black Mountains, 10 to 25 miles west and northwest of Chloride. The Mockingbird, Pyramid, and Pilgrim camps are on the eastern slope; the Virginia camp is on the western slope.
Gold was discovered in 1904 in the Pilgrim camp; however, miners had found gold as early as 1892 in the Gold Bug camp, several miles north of the Weaver district (Schrader, 1909, p. 214, 217). Incomplete production records credit the district with about 1,900 ounces of gold before 1932 (Nolan, in Hewett and others, 1936, p. 17, 19). The period of greatest activity was 1932-42, after which the district declined to the extent that only 138 ounces of gold was reported for 1943-59. Total gold production of the district through 1959 was about 63,200 ounces.
The oldest rocks of the district are Precambrian granite, gneiss, and schist, which are exposed mainly along the eastern slope of the Black Mountains and are overlain on the west slope by Tertiary volcanic rocks intruded by porphyry dikes (Wilson and others, 1934, p. 78-79). The ore, which yields native gold and small amounts of silver, is in veins chiefly in the volcanic rocks. The gangue is quartz, adularia, calcite, and local hematite.