Turquoise is an opaque copper-aluminum phosphate mineral with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It is prized for its blue to green coloration, which results from the presence of copper (blue tones) and iron (green tones). Turquoise typically forms in arid, oxidized environments as a secondary mineral in copper-rich rock.
Features:
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Composition: A hydrated phosphate of copper and aluminum, turquoise is part of the triclinic crystal system but typically forms as microcrystalline masses rather than distinct crystals.
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Coloration: The blue-to-green color spectrum is influenced by varying copper and iron content, with no two specimens exactly alike.
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Formation: Turquoise develops through the weathering and oxidation of copper ore deposits, often in host rocks like sandstone, shale, or volcanic tuff.
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Geologic Sources: Major sources include the southwestern United States (especially Arizona and New Mexico), Iran, Egypt, and China.
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Physical Properties: With a Mohs hardness of 5–6, turquoise is relatively soft and porous compared to other gemstones. Stabilization is sometimes used to improve durability.
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Educational Value: Ideal for studying mineral alteration, phosphate mineralogy, and the geologic conditions required for secondary mineral formation.
These specimens offers a vibrant example of how geochemical processes in arid climates can produce one of Earth’s most historically significant minerals.
