
gemstone
Turquoise (likely stabilized or composite)
Turquoise, hydrated copper aluminum phosphate — CuAl₆(PO₄)₄(OH)₈·4H₂O
AI-generated identification · may be incorrectBlue to blue-green, typically waxy to subvitreous luster; Mohs hardness 5–6, triclinic structure, no prominent cleavage, and specific gravity about 2.6–2.8. The specimen appears set in silver and may contain dark matrix or treated material.
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Physical properties
Blue to blue-green, typically waxy to subvitreous luster; Mohs hardness 5–6, triclinic structure, no prominent cleavage, and specific gravity about 2.6–2.8. The specimen appears set in silver and may contain dark matrix or treated material.
Formation & geological history
Forms as a secondary mineral in arid, copper-rich zones through groundwater alteration of aluminum- and phosphorus-bearing rock, commonly during the Cenozoic. The image shows a polished cabochon rather than its host rock.
Uses & applications
Used chiefly in jewelry and ornamental objects. Commercial turquoise is often stabilized with resin, dyed, reconstituted, or mounted as a cabochon.
Geological facts
The blue color comes mainly from copper; greener tones commonly reflect iron or dehydration. The dark web-like pattern may be natural matrix, though appearance alone cannot distinguish it from added matrix or composite turquoise.
Field identification & locations
Common sources include Iran, southwest United States, China, Chile, and Mexico; it is not especially diagnostic of the Lisbon-area region. Field tests include hardness and density, but avoid scratching jewelry—laboratory testing is needed to detect treatments.
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