metamorphic

Polished lapis lazuli slab

Lapis lazuli; primarily lazurite (Na₃Ca(Si₃Al₃)O₁₂S), with calcite and pyrite

AI-generated identification · may be incorrect

Deep ultramarine-blue, fine-grained, opaque, with subdued vitreous-to-waxy luster; hardness about 5–5.5 Mohs, typically massive rather than visibly crystalline, and no prominent cleavage. The faint gray-white bands likely indicate calcite, while tiny brassy specks would be pyrite.

Identified September 3, 2026More metamorphic →

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Physical properties

Formation & geological history

A metamorphic rock formed when limestone or dolostone was altered by silica-, sulfur-, and aluminum-rich fluids, commonly during contact metamorphism. Commercial-quality material is especially famous from Afghanistan, with deposits also in Chile, Russia, Pakistan, and the United States.

Uses & applications

Used for beads, cabochons, carvings, decorative slabs, and ornamental objects; historically ground as ultramarine pigment. It is valued more for vivid color and minimal calcite than for high transparency.

Geological facts

The name derives from Persian-Arabic terms meaning “blue stone.” Blue color comes chiefly from sulfur-bearing lazurite; excessive white calcite lowers gem value, while pyrite inclusions can enhance collectibility.

Field identification & locations

Identify by its rich blue color, opaque massive texture, possible white calcite veining, and metallic-gold pyrite flecks; avoid confusing dyed sodalite or glass. This strongly blue polished piece is likely lapis lazuli, though testing or provenance is needed for certainty.