mineral

Tumbled red jasper or mahogany obsidian

Microcrystalline quartz (SiO₂), likely jasper; alternative: volcanic glass (obsidian)

AI-generated identification · may be incorrect

Small polished dark reddish-brown specimen with subdued luster; image resolution prevents certainty. Jasper has Mohs hardness ~6.5–7 and no cleavage; obsidian is ~5–5.5, amorphous, and may show glassy conchoidal fracture.

Identified September 7, 2026More mineral →

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Physical properties

Formation & geological history

Red jasper forms when silica-rich fluids cement iron-oxide-bearing sediments, commonly in Precambrian to younger volcanic-sedimentary settings. Mahogany obsidian forms by rapid cooling of rhyolitic lava, generally in Cenozoic volcanic regions.

Uses & applications

Used as a lapidary stone for cabochons, beads, carvings, and tumbled specimens; common pieces have modest decorative value.

Geological facts

The reddish color usually comes from hematite or other iron oxides. A steel file can scratch obsidian more easily than jasper, while jasper typically scratches glass.

Field identification & locations

Commonly found in volcanic and sedimentary terrains worldwide, including the western United States, Mexico, Brazil, and Madagascar. Inspect for granular or opaque texture (jasper) versus uniformly glassy appearance and conchoidal edges (obsidian).