Turquoise

Hardness: 5-6 (Mohs scale), Color: Sky blue to blue-green, Luster: Waxy to subvitreous, Crystal structure: Triclinic (usually cryptocrystalline/massive), Cleavage: Perfect (rarely seen in massive forms), Specific gravity: 2.6-2.9

Formed through the infiltration of meteoric acidic water during the weathering and oxidation of pre-existing minerals (secondary deposit). It is typically found in arid climates within volcanic or sedimentary rocks rich in phosphorus and copper.

Primarily used as a gemstone for jewelry, carvings, and ornamental inlay. It has been used for over 6,000 years by ancient Egyptian, Persian, and Mesoamerican civilizations.

Turquoise is one of the oldest decorative gemstones in human history. The name comes from the French 'turquois' meaning 'Turkish', as the gemstone was historically imported to Europe through Turkey from Persian mines.

Identify in the field by its distinct robin's-egg blue/green color and waxy luster. In this specimen, the dark veins are 'matrix'—fragments of the host rock (likely limonite or manganese oxide). While found globally in arid regions, the reported coordinates (São Paulo, Brazil) are unusual for native turquoise; it is most likely a purchased or transportable specimen, or a lookalike such as dyed howlite or variscite.