The majority of Turquoise mines in Arizona are chiefly open-pit
copper mines, which means that the gemstone has not historically
been their main treasure. Copper miners would alert local contacts
if they hit rich deposits of Turquoise during their days at work,
but it is not uncommon to find it in copper mines - Turquoise is,
after all, a hydrated phosphate of copper and aluminium, which is
how it gets its striking blue hue.
One of the original sources of the Turquoise found on the North
American markets is believed to be Bisbee's Lavender Pit in
Arizona, which is part of the Copper Queen mine there. The
distinctly bright blue stones mined in Bisbee are famous for the
chocolatey brownness of their fine webbing, but they also come in
an impressive deep green colour. A blacker matrix of webbing can be
found in the famous Kingman mine in Arizona, which is where many of
the world's purest stones have been mined. The colour of Kingman
Turquoise is so striking that it is widely deemed to be the
industry standard for comparison.
The southwest USA didn't stop there either; the Sleeping Beauty
mine in Globe, Arizona, has produced some of the highest-grade
Turquoise around and it's up there with the world-renowned Persian
Turquoise from the mines that are now modern-day Iran.