Bisbee is a classic turquoise. The history is found in Turquoise in America Part Two, 1910-1990.
 
This cab weighs 23.1 carat and measures 2.5cm X 2cm. It is priced at $200 a carat or $4620. It is not treated and is backed. I have assigned a TG of 94 or GG. Bisbee of this grade is very rare. I bought this from Bruce Mead who cut the stone. White spot is camera flash.