mineral

Polished chalcedony (likely jasper or agate)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, translucent to opaque, with a waxy-to-glassy luster and no visible cleavage. The specimen is reddish-brown, gray, and cream, with mottled iron staining and a freshly polished surface; exact identification is limited by the image.

Identified August 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities, fractures, or volcanic vesicles and precipitates cryptocrystalline quartz, often with iron oxides. Its age depends on the host rock and cannot be determined visually.

Uses & applications

Used for cabochons, carvings, beads, lapidary items, and ornamental stone; lower-grade material has little industrial significance.

Geological facts

Agate and jasper are varieties or trade descriptions of chalcedony: agate is commonly banded or translucent, while jasper is generally opaque and impure. The brown-red coloration commonly reflects hematite or limonite.

Field identification & locations

Common in volcanic terrains, river gravels, and weathered silica-rich rocks worldwide. Test with a steel file or quartz reference, inspect translucency and banding, and use a specific-gravity or laboratory test for confirmation.