Bisbee turquoise is one of the most famous of all turquoise. It is a byproduct from the Phelps Dodge Lavender Pit copper mine in Bisbee Arizona. The story of Bisbee is found in Turquoise in America Part Two, 1910-1990.
 
This cabochon weighs 20.9 carat and measures 2.25cm X 1.5cm X 6mm. It is priced at $10,ct or $209. It is not treated and is backed. I have assigned a TG of 74 or MG. White spot is camera flash.