Other Names: San Antonio, Santa Clara
Discovered: 1866; 1905
Commodities: gold, silver, antimony, arsenic, tungsten, mercury, nickel, turquoise, fluorspar
According to Ferguson (1924), the southern part of the Toquima Range that is now included in the Manhattan district may once have been part of the San Antonio (San Antone) district. The main Manhattan district lies along Manhattan Gulch on the western side of the southern Toquima Range, but the Pipe Spring, Spanish Spring, Willow Spring, and Baxter Spring areas in the southern Toquima Range are also included in this district.
Silver discoveries were made in 1866 and gold discoveries were made near the old silver camp in 1905. The Santa Clara district (Todd and Welton, 1866), was located in the vicinity of Willow Point on the southwestern tip of the Toquima Range; this area is now included in the Manhattan district.
Todd and Welton, 1866; Angel, 1881, p. 518; Stuart, 1909, p. 86; Hill, 1912, p. 222; Ferguson, 1924, p. 7; Lincoln, 1923, p. 175; Stoddard, 1932, p. 68; Bailey and Phoenix, 1944, p. 145; Kral, 1951, p. 113; Lawrence, 1963, p. 146; Morrissey, 1966, p. 25; Kleinhampl and Ziony, 1984, p. 140; Stager and Tingley, 1988, p. 144
Placer District Description
Southern end of the Toquima Range, on the east side of the Big Smoky Valley, T. 8 N., Rs. 43 and 44 E.
Manhattan and vicinity, special edition, scale 1:24,000.
Ferguson, 1917, Geologic map of the Manhattan district, Nevada, (pi. 6), scale 1:48,000.
From Tonopah, 5 miles east on U.S. Highway 6 to junction with State Highway 8a; from there, 38 miles north to junction with State Highway 69, which leads 6 miles east to Manhattan mining area.
The placers in the Manhattan district were discovered in 1906 and have been the second most productive in the State during this century. These deposits are largely confined to Manhattan Gulch, which trends east-west across the west flank of the Toquima Range, draining the adjacent lode-gold mining area between Gold Hill and Palo Alto Hill.
Gold is found in four types of gravel corresponding to different stages of development of the gulch and adjacent hillsides. The oldest gravels are found in patches on both sides of the gulch at elevations of 20-70 feet above the present gulch level. These gravels are the remnants of an early stage in the development of the gulch before active downcutting of the canyon, and the gold concentration is much lower than that in the younger gravels. Active downcutting of the canyon resulted in the erosion of gold lode from Gold Hill and Palo Alto Hill, and deposition of gold-bearing gravels continued during downcutting of the canyon.
These rich gold-bearing gravels are now seen as bench gravels on the canyon walls and as gravels in the deep channel of Manhattan Gulch. They overlie bedrock and are generally less than 10 feet thick, and are, inturn, overlain by as much as 40-100 feet of relatively barren overburden. These gravels are known to be Pleistocene in age on the basis of fossil remains recovered during placer operations. The youngest placers are found in recent wash on the hillsides, derived from erosion of the under- lying veins.
The placers have been worked for a distance of about 6 miles from the vicinity of Gold Hill (approximately sec. 20, T. 8 N., R. 44 E., unsurveyed) to the eastern edge of the Big Smoky Valley (approximately sec. 21, T. 8 N., R. 43 E., unsurveyed). Detailed studies of the fineness of the placer gold recovered from the gravels (Ferguson, 1917, p. 191) show that the gold increases in fineness from east to west (range from 704 to 738) owing to solution of silver and base metals by the long action of ground water on the gravels, which have been undisturbed since the Pleistocene.
Production history: Since their discovery in 1906, the placers have been worked continuously by several methods in both large- and small-scale operations. Most of the placers in this district were reached by shafts and drifts and worked by sluices and drywashers. The numerous small operations had a significant yearly production.
The most productive epoch in placer mining at Manhattan occurred between 1938 and 1946, when the Manhattan Gold Dredging Co., a subsidiary of Natomas Co. operated a floating bucket-line dredge which had 108 9 1/2 cubic foot buckets in Manhattan Gulch. The water for the operation was obtained from a 12-mile-long pipeline originating at Peavine. The dredge started at the eastern edge of the Big Smoky Valley (approximately sec. 21, T. 8 N., R. 43 E., unsurveyed) and worked eastward about 5 miles up the gulch to approximately the mouth of Black Mammoth Gulch (sec. 19, T. 8 N., R. 44 E., unsurveyed).
Barren overburden averaged 30 feet deep. Both gulch gravels and bench gravels were dredged, the latter being pushed into the dredge path by large tractors, bulldozers, and scrapers. The company was given permission to operate at a reduced scale during wartime (1943-45). The dredge ceased operations at the end of 1946 and was later shipped to Copper Canyon, Lander County (seep.37-38), where it was used in other large placer-mining operations.
Because mining took place after 1905, we have a reasonably complete record of the amount of placer gold recovered from the district. Recorded production indicates that $6,342,796 in placer gold was recovered between 1907 and 1967. The actual true placer production probably is not less than $7 million, as an unknown amount of placer gold produced was certainly not reported to the Government over this 60-year period. The dredge operation recovered somewhat less than 133,608 ounces of the total gold produced, and small-scale operations have recovered, over the entire 60-year period, at least 73,290 ounces.
The placer gold in the Manhattan district was derived from the gold veins in the district, especially those at Gold Hill. The veins at Gold Hill occur in Cambrian limestones and schists of the Gold Hill Formation. Most of the placer gold is thought to be derived from the numerous, closely spaced quartz stringers in the schist rather than from the gold-bearing narrow fissures and replacement deposits in the limestone. The age of mineralization is thought to be early Tertiary or pre-Tertiary, the age of northwest-trending prevolcanic faults in the area.
Clark, 1946: Describes techniques of placer mining used during large-scale operations; describes dredge, water supply, recovery methods; indicates extent of ground worked.
Ferguson, 1917: Detailed description of placers; includes history, production, mining operations; discusses development of present topography, distribution of gold in old gravels, deep gravels, and recent wash; size and fineness of placer gold; accessory minerals. 1924: Brief account of placer occurrences summarized from Bulletin 640-J (1917), including maps, distribution of gold, character of gold, stream studies relating to size distributions of gold.
Ferguson and Cathcart, 1954: Text summarizes earlier study of Manhattan district (Ferguson, 1924).
Jones, 1909: Reviews geology of district; describes early placer-mining activity; lithology, thickness, and value of placer gravels; mining op- erations in 1909; includes claim maps of placer areas; average value of ground reported to be $10 per cubic yard.
Krai, 1951: Detailed description of history, geology, lode and placer mines of the district; much information taken from earlier writers. Adds information of production of placers to 1949, history of large- scale placer operations during the period 1938—46 and subsequent small-scale operations to 1949.
Martin, 1912: Production for 1911; depth and value of placer gravels; placer-mining techniques (paper similar to Toll, 1911).
Mining and Engineering World, 1913a: Describes drywash placermining plant owned by Thomas Wilson; extent and number of pay streaks in gulch worked.
Mining World, 1941b: Details of dredge and stripping operations in Manhattan Gulch; depth of barren overburden; total depth of dredgeable ground; details of stripping benches that dredge cannot reach; distribution of gold-bearing gravel; size of gravel; size of gold.
Paher, 1970: Photographs include many of early townsites and one of a dredge that operated near mouth of Manhattan Gulch; history of mining activity at Manhattan.
Stoneham, 1911: Describes rich placer gravels in main gulch below Manhattan discovered in April 1909; extent and thickness of gravels; placer-mining operations; drywash plant owned by Thomas Wilson described; value of gravels; presence of gold in dry lakebed in Smoky Valley.
Toll, 1911: Placer production for past year (1910-11) ; average thick- ness of gravel and pay streak; average value per yard in pay streak; methods of working placers.
U.S. Geological Survey, 1969: Relation of mineral deposits to faults and age of mineralization.
Vanderburg, 1936a: History and production of district; extent of placers; size of nuggets found; placer-mining techniques and methods to 1935; placer sampling by Natomas Co. described.