metamorphic
Tumbled lapis lazuli
Lapis lazuli; predominantly lazurite, (Na,Ca)₈(AlSiO₄)₆(S,SO)₄, with calcite and pyrite
AI-generated identification · may be incorrectDeep blue, opaque, with lighter calcite veining and possible brassy pyrite flecks; vitreous to dull luster, granular structure, no prominent cleavage, Mohs hardness about 5–5.5, specific gravity 2.7–2.9.
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Physical properties
Deep blue, opaque, with lighter calcite veining and possible brassy pyrite flecks; vitreous to dull luster, granular structure, no prominent cleavage, Mohs hardness about 5–5.5, specific gravity 2.7–2.9.
Formation & geological history
A metamorphic rock formed when limestone is altered by silica- and sulfur-rich fluids, commonly during contact metamorphism; major deposits are Precambrian in age, especially Afghanistan. This rounded piece has been polished or tumbled.
Uses & applications
Used for cabochons, beads, carvings, ornaments, and occasionally ultramarine pigment; not generally used in construction. Value depends strongly on saturated blue color, low calcite, and visible pyrite.
Geological facts
The finest lapis is intense, even royal blue with minimal white calcite. Historically, powdered lapis supplied natural ultramarine pigment used in medieval paintings.
Field identification & locations
Identify it by its opaque royal-blue color, white calcite streaks, and occasional metallic-gold pyrite; unlike dyed howlite, it is typically dense and nonporous. Common sources include Afghanistan, Chile, and Russia.
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