Turquoise (beads)

Hardness: 5-6 (Mohs); Color: Sky blue to blue-green, sometimes yellowish-green; Luster: Waxy to subvitreous; Crystal Structure: Triclinic (typically cryptocrystalline masses, rarely distinct crystals); Cleavage: Perfect on {001} and {010}, but rarely seen due to massive habit; Specific Gravity: 2.6-2.9

Turquoise is a secondary mineral formed by the alteration of pre-existing aluminum-rich rocks in arid regions. It precipitates from aqueous solutions that contain copper, aluminum, and phosphate, usually in fractures and cavities. Its formation is typically associated with volcanic rocks that have undergone extensive weathering. Geological age varies depending on the deposit, but many prominent deposits are found in relatively young (Cenozoic) volcanic or sedimentary rocks.

Predominantly used as a gemstone for jewelry (necklaces, bracelets, rings, earrings) due to its attractive blue-green color. It's also used for ornamental carvings and inlays. Historically, it has been used in spiritual and cultural artifacts across various civilizations.

Turquoise has been valued as a gemstone for thousands of years, with archaeological evidence of its use dating back to ancient Egypt (around 3000 BCE) and Persia. The name 'turquois' is believed to derive from the French word for 'Turkish', as it was first brought to Europe from Turkey. Its color can fade or change over time when exposed to sunlight, sweat, or oils, a process known as 'sweating' or 'greening'.

In the field, turquoise is typically identified by its distinctive blue-green color, often with a matrix of host rock (usually dark gray or brown). It is found in arid and semi-arid regions worldwide. Important deposits are in Iran (historical Persian turquoise), the Southwestern United States (Arizona, New Mexico, Nevada), China, Egypt, Mexico, and Chile. It often occurs as nodules, vein fillings, or crusts. Identifying natural untreated turquoise can be challenging as it is frequently treated (stabilized, dyed, or impregnated) or simulated by other minerals or plastics. A scratch test (hardness 5-6) can help distinguish it from softer materials. Experienced collectors often look for the natural matrix patterns and characteristic waxy luster.