metamorphic
Lapis lazuli (likely)
Lapis lazuli, a rock composed mainly of lazurite (ideally (Na,Ca)₈(AlSiO₄)₆(S,SO₄,Cl)₂), with calcite and commonly pyrite
AI-generated identification · may be incorrectDeep blue with pale calcite-rich streaks; lazurite has a vitreous to greasy luster, Mohs hardness about 5–5.5, and a complex cubic structure. The small, rough fragment shows no obvious pyrite; visual identification is not definitive.
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Physical properties
Deep blue with pale calcite-rich streaks; lazurite has a vitreous to greasy luster, Mohs hardness about 5–5.5, and a complex cubic structure. The small, rough fragment shows no obvious pyrite; visual identification is not definitive.
Formation & geological history
Forms by contact metamorphism of limestone, typically in marble deposits; notable deposits formed in Afghanistan’s Hindu Kush, with other occurrences in Chile and elsewhere. The specimen’s age and source cannot be determined from the image.
Uses & applications
Used for beads, carvings, inlay, and ornamental objects; historically ground into ultramarine pigment. Lower-grade material is commonly sold as rough pieces or tumbled stone.
Geological facts
The bright blue mineral lazurite gives lapis its color, while white calcite lowers its grade; gold-colored pyrite flecks are common but not required.
Field identification & locations
Likely lapis lazuli, but sodalite or dyed material can look similar; check for natural calcite veining and avoid relying on color alone. A hand-sized rough fragment of this apparent grade might sell for about $5–$30, depending on authenticity, weight, and quality.
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