mineral

Polished tektite (likely indochinite)

Impact glass; natural silica-rich glass, approximately SiO₂ 70–80%

AI-generated identification · may be incorrect

Black to dark brown, vitreous-to-waxy luster, conchoidal fracture, no cleavage, and hardness about 5.5–6.5 Mohs; commonly vesicular and sculpted, as shown. Specific gravity is typically about 2.3–2.6.

Identified September 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed when a large meteorite impact melted and rapidly quenched terrestrial surface rocks roughly 0.78 million years ago; Southeast Asian tektites are associated with the Australasian impact event.

Uses & applications

Primarily a collector specimen, lapidary material, and occasional jewelry stone; it has little industrial value.

Geological facts

Tektites are natural glasses, not ordinary volcanic obsidian, and their aerodynamic shapes can result from molten droplets flying through the atmosphere. The smooth surface here appears polished or tumbled.

Field identification & locations

Identify by its low density, glassy appearance, conchoidal fracture, bubbles, and lack of crystals; common sources include Vietnam, Thailand, Cambodia, Laos, and southern China. Confirm with laboratory chemistry or microscopic study, since black slag and obsidian can look similar.