Turquoise
CuAl6(PO4)4(OH)8 · 4H2O · Semi-Precious Gemstone / Ornamental and Collector Mineral
Crystal System
Triclinic system, rarely forms distinct crystals; typically occurs as massive, microcrystalline, cryptocrystalline aggregates, nodules, veins, or crusts.
Mineral Group
Phosphates, specifically an anhydrous phosphate with subordinate hydroxyl and water.
Chemical Formula
CuAl6(PO4)4(OH)8 · 4H2O (Hydrated copper aluminum phosphate)
Formation Process
Supergene (secondary) alteration process formed by the weathering and oxidation of pre-existing copper deposits and aluminum-bearing rocks in arid, oxidizing environments near the surface.
About This Crystal
The specimen is a rounded, cabochon-cut green turquoise set within a decorative vintage-style sterling silver ring. The stone exhibits a predominantly medium green body color with visible matrix webbing containing brownish to dark inclusions, showing an opaque transparency and a waxy to sub-vitreous luster.
Physical Characteristics
Color ranges from robin's egg blue to greenish-blue and apple green, with a white or pale green streak. It has no distinct cleavage, exhibits a conchoidal to uneven fracture, a specific gravity of 2.60-2.90, and a waxy to dull tenacity making it somewhat brittle.
Optical Properties
Biaxial (+) with refractive indices ranging from approximately 1.61 to 1.65. It is doubly refractive with a weak birefringence and no significant pleochroism, generally displaying an opaque character with scattered surface light reflection.
Hardness & Durability
Origin Region
Notable sources include the southwestern United States (Arizona, Nevada, New Mexico), Iran (Nishapur), China, and the Sinai Peninsula. Forms in arid regions where acidic copper-rich groundwater reacts with aluminum- and phosphorus-bearing minerals.
Hardness & Durability
Mohs hardness of 5 to 6, making it moderately soft and vulnerable to scratching by harder minerals, quartz, and steel. It has fair to poor toughness and can be porous, absorbing oils, cosmetics, and harsh chemicals.
Care & Maintenance
Clean gently using warm, soapy water and a soft cloth; avoid ultrasonic cleaners, steam cleaners, harsh chemicals, abrasive materials, and prolonged exposure to oils, perfumes, and direct sunlight which can alter its color.
Rarity & Value
Common to Uncommon, highly dependent on origin, color saturation, lack of heavy matrix, and absence of stabilizing treatments. High-grade untreated natural turquoise commands premium collector prices.
Special Characteristics
Frequently features spiderweb or limonite/sandstone matrix inclusions that create unique natural patterns across the stone's surface, enhancing its individual aesthetic appeal.
Lore & History
Historically revered by Native American, Ancient Egyptian, and Persian civilizations as a sacred stone of protection, good fortune, and healing. In modern crystal healing, it is associated with the throat chakra, promoting communication, tranquility, and spiritual grounding, though these are traditional beliefs and not scientifically proven.