Kingman, in Mohave County, Arizona, gives its name to the Kingman Turquoise Mine and to the broader district of copper-bearing porphyry deposits in the Cerbat Mountains north and east of the town. The town was founded in 1882 along the Atlantic and Pacific Railroad and named for Lewis Kingman, the surveyor who laid out that section of the route. From a gemmological standpoint the locality is significant chiefly for one ore-body: the Mineral Park porphyry copper deposit, in which the Kingman turquoise vein system has been worked since the late nineteenth century.

Geological setting

The Mineral Park deposit is a Laramide-age porphyry copper system emplaced into Precambrian schist and granite. Turquoise occurs in the upper, supergene-altered zone of the deposit, where weathering of primary chalcopyrite supplied copper to descending phosphorus and aluminium-bearing groundwaters. The resulting turquoise forms vein-lets and nodules within altered host rock, frequently in close association with quartz and the iron-rich limonitic matrix that gives much Kingman material its characteristic dark webbing. Pre-Columbian working of the deposit is documented archaeologically; commercial extraction in the modern sense dates from circa 1880 and has been substantially continuous, with the turquoise operation now functioning as a by-product of the larger copper mine.

Significance to the gem trade

Through the twentieth century Kingman became one of the most prolific sources of high-grade turquoise in the United States, with output sufficient to anchor a stable trade in untreated and lightly stabilised material. The mine has been worked under several successive owners; the Colbaugh family has been the principal turquoise lessee since the mid-twentieth century. For the broader locality entry, see the related article on Kingman turquoise for a treatment of the gem material itself, its colour ranges, and its place in the American Indian and contemporary jewellery trades.

Other gem occurrences

Beyond turquoise, the Kingman district has produced minor amounts of chrysocolla, malachite and azurite from the same supergene zone, and the broader Cerbat range has yielded fluorite and several lead-zinc minerals of mineralogical rather than gem interest. Native gold has been recovered historically from placers in the Mohave Wash drainage but in quantities small enough that the locality is not commonly cited in jewellery contexts.