Blue Diamond is a famous turquoise mine in Lander County Nevada. The story is told in Turquoise in America Part Two.
 
This cabochon weighs 26.1 carat and measures 2.5cm X 2cm X 7mm. The price is $60/ct or $1566. It is not treated and is backed. I have assigned a TG of 85 or HG. I purchased this stone from the Tony Mancini. White spot is camera flash.