From TFA: "But there are still no known turquoise deposits in Mesoamerica. The explanation, say Thibodeau and her colleagues, is that turquoise deposits tend t

From TFA: "But there are still no known turquoise deposits in Mesoamerica. The explanation, say Thibodeau and her colleagues, is that turquoise deposits tend to be shallow, and they can be mined to depletion in short order. And there are copper deposits all over Mesoamerica. Thibodeau and her colleagues said the turquoise mines that supplied the Aztecs may have been mined out well before Europeans set foot on the continent."