Thursday, 9 March 2017

California Turquoise

Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium. It is rare and valuable in fine grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue.

In recent times, turquoise has been greatly devalued, like most other opaque gems, by the introduction of treatments, imitations, and synthetics.

The production of turquoise from deposits in California can be traced back to pre-Colombian Native Americans. Prehistoric mining tools have been found in some of the old workings of the turquoise mines. Over the years, the State's deposits have produced a substantial amount of turquoise. Deposits are located in San Bernardino, Imperial, and Inyo Counties. The material occurs as nodules and as vein filling.
In the better grade materials, the color varies from a pale to a dark blue, poorer grade materials are greenish-blue and green in color.
Historically, a number of turquoise mines operated in the State, several mines in each of the counties. Today, only a very few mines still produce commercial Turquoise, none of which is easy to find.

California turquoise is no longer marketed in large commercial quantities, but high grade examples can still be found by amateur rock hunters.