Turquoise

Hardness: 5-6 (Mohs scale); Color: Sky blue to blue-green; Luster: Waxy to sub-vitreous; Crystal Structure: Triclinic; Cleavage: Perfect (rarely seen in massive form); Specific Gravity: 2.6–2.9

Formed by the percolation of acidic aqueous solutions during the weathering and oxidation of pre-existing minerals. It is typically found in arid climates as veins or crusts within altered volcanic rocks (such as rhyolite or trachyte) or sedimentary rocks.

Predominantly used as a gemstone for jewelry (cabochons, beads, and inlays) and for ornamental carvings. It has deep cultural and religious significance in Native American and Persian traditions.

Turquoise is one of the oldest known gemstones, used by the Ancient Egyptians as early as 3000 BCE. Its name is derived from the French 'turquois' meaning 'Turkish', as it was historically brought to Europe through Turkey from mines in Persia.

Identify in the field by its distinct robin's egg blue color and its association with copper deposits (limonite or quartz host stone). Common locations include the Southwestern USA (Arizona, Nevada, New Mexico), Iran, China, and Egypt. Collectors should look for 'matrix' (host rock inclusions) which can help identify the specific mine of origin.