Turquoise

Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue.

Turquoise in "Eyewear"
Estevánico prized turquoise. During the Coronado Expedition, Estevánico often used his magical eyewear to help heal various natives he encountered. He took turquoise and a woman as payment for his services.

After his eyewear was stolen, Estevánico arrived at Hawikuh, where he demanded turquoise and a woman from the Zuni as a price to keep the Spanish from the attacking the Pueblo. The Zuni didn't belive him, and murdered him.