King of Arizona Mine, Kofa Mining District, Yuma County, Arizona, USAi

Regional Level Types
King of Arizona Mine	Mine
Kofa Mining District	Mining District
Yuma County	County
Arizona	State
USA	Country

A former underground Au-Ag(58:1)-Mn mine located on 4 full claims (Homestake; King of Arizona; Last Hope; Mucho Bueno) in the center of sec. 12, T2S, R17W, south end of the Kofa Mountains, on federal land. This mine is partially on the Homestake claim, which covers the chief workings of the mining operation. Outcrops at an elevation of about 1,700 feet above sea level. Discovered by Charles E. Eichelberger. Owned at times, or in part, by the King of Arizona Mining & Milling Co.; Rob Roy Development Co.; and the Kofa Mining Syndicate. Operated by Barons Gold, Inc., Lethbridge, Alberta, Canada (1986). Started winter 1896 and closed Jan 1899. Reopened August 1899 and ceased operations about July, 1910. Last produced 1939.

Mineralization is fine-grained free gold with silver in a layered quartz gangue in an irregular fissure vein (King of Arizona vein) in a large shear zone cutting Cretaceous or Tertiary rhyolite volcanics and silicified, brecciated andesite. The lode is 670.56 meters long, 3.66 meters wide, with a depth to top of 0 meters, is 228.6 meters thick, and trends between N.60ºW. & West and dips at an angle of 60ºS. The orebody is said to average 12 feet wide. Lode matter is a brecciated, generally brown to maroon andesite porphyry. The andesite is partly silicified, particularly where fissuring is closely spaced. There are many quartz and manganocalcite stringers that traverse the lode in all directions, from knife-blade thick to several feet wide. Vein width increases with depth but with decreasing values.

A strong vein of gold-bearing quartz. The vein width increases with depth but with decreasing values. The footwall of the vein is generally a well-defined slicken-sided plane, but the hanging wall is indefinate. The ore body contained many small fissures and small slip planes, and most of them are parallel to the trend of the ore body, but several lie at angles with the vein, generally coming in from the hanging wall side, and make horses of barren material. About 200 feet east of the shaft strong cross-fissures filled with calcite apparently limit the ore. There are 3 well-marked divisions or layers within the vein. On the hanging wall there is a soft layer from 3 to 3½ inches (7.5 to 9 cm) wide averaging $800 Au/T (period values). Next, below this is a middle layer or body of quartz about 20 inches (50 cm) thick averaging about $190-200 Au/T (period values). The remainder of the vein averages $24 Au/T (period values). The vein is crosscut West of the shaft & proved to be 18 inches wide (45 cm) The lode trends between N.60ºW. & West and dips about 60ºS.

Workings are extensive underground with stopes from surface to the 750 foot level serviced by a 750 foot (228 meters) deep inclined shaft. Drifts on the 100 foot level and an adit at the collar level. Drifts West of the shaft are over 2,000 feet long; while on the East they are not longer than 200 feet. This mine was worked from the late 1880's to 1910, and sporadically through 1937. It produced some 739,300 tons of ore averaging about 0.23 oz. Au/T and 0.1 oz. Ag/T, valued at 3,500,000 in Au (period values). Barons constructed an agitation leach facility and began production in late 1986 from tailings.

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Link to USGS MRDS:	10027228

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