Provenancing turquoise: a difficult task

Turquoise is a blue-green phosphate gem used for millennia in the lapidary artwork of numerous past societies. It was one of the first gemstones, and has proved to be a valuable material that was part of long-distance exchange networks on every continent where it is available. Nonetheless, provenance studies for this material is absent from gemological literature, and scarce in the archaeological literature. This work reviews the mineralogy, geology, geographical and archaeological distribution of this gemstone, and presents different mineralogical, geochemical and spectroscopic approaches used in provenance studies. Sophisticated methods are needed to reconstruct the origin of turquoise and the commercial networks in the ancient times for this lapidary raw material, and we show that, even with these methods, a lot of work still remains to be done.