metamorphic
Blue-and-gold lapis lazuli fragment
Lapis lazuli; lazurite-rich calc-silicate rock (primarily lazurite, with calcite and pyrite)
AI-generated identification · may be incorrectTypically deep ultramarine blue with white calcite and brassy pyrite flecks; Mohs hardness 5–5.5, vitreous to dull luster, opaque, massive rather than distinctly crystalline, and no obvious cleavage.
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Physical properties
Typically deep ultramarine blue with white calcite and brassy pyrite flecks; Mohs hardness 5–5.5, vitreous to dull luster, opaque, massive rather than distinctly crystalline, and no obvious cleavage.
Formation & geological history
Formed by contact metamorphism of carbonate rocks, commonly marble, during intrusion of igneous bodies; prized deposits in Afghanistan are Paleozoic–Mesozoic in age. The visible specimen is likely tumbled or polished.
Uses & applications
Used for beads, cabochons, carvings, ornaments, and the historic pigment ultramarine; lower-grade material is used for decorative stone. Small polished pieces have modest collector value.
Geological facts
The richest blue color comes from lazurite, while pyrite produces the characteristic gold specks; excessive white calcite generally lowers gem quality.
Field identification & locations
Identify it by its opaque royal-blue color, contrasting calcite veining, and metallic-gold pyrite inclusions; it is commonly found in Afghanistan, Chile, Russia, and Tajikistan. A small polished chip like this is typically worth $2–$15 USD, with exceptional deep-blue material worth more.
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