Location
The Las Guijas and San Luis Mountains, Tps. 20 and 21 S., Rs. 9 and 10 E.
Topographic Map
Arivaca 15-minute quadrangle.
Geologic Map
Wilson, Moore, and O'Haire, 1960, Geologic map of Pima and Santa Cruz Counties, scale 1:375,000.
Access
From Arivaca Junction on U.S. Highway 89, it is 23 miles west on light-duty road to Arivaca. Many roads lead to placer areas in the surrounding mountains.
Extent
Placer gold has been found in most of the gravels that mantle the flanks of the Las Guijas Mountains and in many gulches that head in the mountains. Most of the placer mining was concentrated on the northeast flank of the range, south of Las Guijas Creek; here, mesa gravels between the edge of the mountains and the creekbed are notably gold bearing for a length of 2 1/2 miles and a width of 1 mile (sec. 25, T. 20 S., R. 9 E., sees. 30-32, T. 20 S., R. 10 E.).
Durzano and Pesqueria Gulches (sec. 32, T. 20 S., R. 10 E.; sec. 5, T. 21 S., R. 10 E.) also contain placer gold.
Placers are found in the gravels in large basins and wide arroyos on the southern slope of the Las Guijas Mountains, northeast of Arivaca Wash (NE 1/4 and NW 1/4 T. 21 S., Rs. 9 and 10 E.). Apparently the gold in these gravels, in contrast to the placers on the north side of the mountains, is irregularly distributed.
Farther south, in San Luis Canyon (vicinity of the SE. cor. T. 21 S., R. 9 E.), placers are reported in some interarroyo bench gravels on the dissected pediment in that area.
Production History
The placers in the Arivaca district have been worked since, and possibly before, the 1850's. The occurrence of placer gold in the region was so well known that the mountains were named "Guijas," which means rubble or conglomerate in which placer gold is usually found. The early production of placer gold from the area is unknown, but it has been estimated to be about $150,000.
In the 1850's Ignacio Pesqueria and a band of followers defeated in a revolution in Mexico fled to the Las Guijas area, where they obtained sufficient gold from the gravels to finance another revolution that in 1856 enabled Pesqueria to become Governor of the State of Sonora, Mexico.
Since that time, placer mining has continued in the district with varying degrees of intensity. In 1905 the New Venture Placer Mining Co. made plans to mine the gravels by hydraulic techniques after sampling that indicated an average of $1.69 per cubic yard on tests of 4,800 cubic yards but apparently did not begin operations. The same company mined the placers in Durzano, Pesqueria, and Yaqui Gulches in 1915 with a Clark agitating sluice, which uses small amounts of water.
Later, in 1983, the pediment and gulch gravels at the northern foot of the Las Guijas Mountains were worked on a large scale; the gold-bearing gravels contained much black sand and some cinnabar. Placer wolframite was recovered from gravels in the low range of hills north of Las Guijas Creek.
Source
The geology of the Arivaca district is poorly known. Many prospects and mining claims are located in the Las Guijas Mountains, and the placer gold was undoubtedly derived from local gold-bearing veins, the occurrence and nature of which is unknown.
Literature
Allen, 1922: Location; extent of placer gravel; source; thickness of gravel; distribution, size, and shape of gold particles; placer-mining operations; gold values per cubic yard.
Bryan, 1925: Definition of "Guijas."
Trippel, 1888: Notes placer-mining activity.
Willis, 1915: Location; history; production estimates; thickness and extent of placer gravels; character of gold particles; grades of gravel; distribution or gold in gravel.
Wilson, 1941: Reports wolframite placers.
1961: Location; history, placer-mining activity during the period 1932-33; source.
