sedimentary

Polished jasper or chert pebble

Microcrystalline quartz (SiO₂), likely iron- and clay-rich jasper/chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; yellow-brown to olive-gray, opaque, with a waxy-to-glassy luster and conchoidal fracture. The rounded, glossy surface appears naturally water-worn and possibly polished or coated.

Identified September 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediments, often incorporating iron oxides and clay that produce yellow, brown, and gray colors. Such material commonly formed in sedimentary or volcanic environments over millions of years; the specimen’s exact age is indeterminate.

Uses & applications

Used as a lapidary stone for cabochons, carvings, beads, and polished display pieces; generally little industrial value in small specimens.

Geological facts

Jasper and chert are varieties of cryptocrystalline quartz, so individual quartz crystals are usually invisible. Color zoning and opaque silica distinguish it from ordinary translucent chalcedony.

Field identification & locations

Common in river gravels and silica-rich formations worldwide; identify by its very high hardness, lack of cleavage, opaque fine-grained texture, and conchoidal fracture. A steel file should barely scratch it, while it can scratch ordinary glass.