This is an Authentic Natural Smoky Bisbee Turquoise Cabochon that is from the Durango Silver Company. This means it is from the Bob Mathews / Cecil Mickelson collection - they were the only two people that had rights to mine Turquoise at the Bisbee Mine, whice was from 1965 to 1977. This stone has great charicter with Bisbee Blue Turquoise and chocolate brown matix that Bisbee is so famous for. It measures approximatel 16.5mm x 28mm and weighs 27 carats. It is priced at $15.00 per carat which is a great buy!