turkuaz

Turkuaz, commonly known in English as turquoise, is both a blue-green color and a mineral gemstone. The name turquoise in English derives from Old French pierre turquoise, literally “Turkish stone,” reflecting how the gem was imported into Europe via Turkish traders from mines in the region that is now Iran and the southwestern Asian mountains. In Turkish, the color and gemstone are called turkuaz.

The gemstone is copper aluminum phosphate with the formula CuAl6(PO4)4(OH)8·4H2O. It is relatively soft, 5–6 on the Mohs scale, with a waxy to silky luster. Color ranges from sky blue to greenish blue; the vivid blue tone is associated with copper, while iron or chromium can shift hues toward green or yellowish tones. The matrix in which turquoise occurs can show brown, black, or gray veining.

Formation and sources: turquoise is a secondary mineral formed by weathering and groundwater that transports copper and aluminum phosphate in arid environments. Common sources include Iran (Khorasan province), the southwestern United States (Arizona, Nevada, including deposits such as Sleeping Beauty and Kingman), Egypt, China, and Mexico.

Uses and care: turquoise has been used in jewelry and decorative objects since ancient times and remains popular in various cultures. Some turquoise is stabilized with resin or polymer to improve durability, while natural forms may be treated to enhance color. It should be protected from oils and solvents; cleaning with mild soap and water is typically recommended.