The Collaborative International Dictionary
bone turquoise
Odontolite \O*don"to*lite\, n. [Odonto- + -lite.] (Min.) A fossil tooth colored a bright blue by phosphate of iron. It is used as an imitation of turquoise, and hence called bone turquoise.
Wiktionary
bone turquoise
n. fossil bone or tooth of a delicate blue colour, sometimes used as imitation turquoise