page_title: Turquoise
section_title: Occurrence
hierarchical_section_title: Turquoise / Occurrence
caption_attribution_description: Cutting &amp; grinding turquoise in Mashhad, Iran.
context_page_description: Turquoise is an opaque, blue-to-green mineral that is a hydrated 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 gemstone and ornamental stone for thousands of years owing to its unique hue. Like most other opaque gems, turquoise has been devalued by the introduction onto the market of treatments, imitations and synthetics.
  The gemstone has been known by many names. Pliny the Elder referred to the mineral as callais and the Aztecs knew it as chalchihuitl. The word turquoise dates to the 17th century and is derived from the French turquois meaning "Turkish" because the mineral was first brought to Europe through Turkey, from mines in the historical Khorasan of Iran.
context_section_description: Turquoise was among the first gems to be mined, and many historic sites have been depleted, though some are still worked to this day. These are all small-scale operations, often seasonal owing to the limited scope and remoteness of the deposits. Most are worked by hand with little or no mechanization. However, turquoise is often recovered as a byproduct of large-scale copper mining operations, especially in the United States.
caption: Cutting and grinding turquoise in Nishapur, Iran, 1973
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