sedimentary

Polished banded chert or jasper

Microcrystalline quartz (SiO₂), likely iron- and manganese-stained chert/jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; dark brown, gray, and cream bands with a dull to waxy luster and very fine-grained, cryptocrystalline structure. It appears smoothly tumbled or polished, with no obvious cleavage and conchoidal-fracture potential.

Identified September 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed from silica-rich sediment or chemically precipitated/cherty layers, later colored by iron or manganese oxides; commonly Paleozoic to Precambrian, depending on locality. The rounded shape is human-produced by tumbling or natural abrasion.

Uses & applications

Used for cabochons, beads, carvings, decorative stone, and small collector specimens; chert was historically important for tools and fire-making. This piece has modest lapidary value.

Geological facts

The boundary between chert and jasper is informal: jasper is typically more opaque and impurity-rich, while chert may be gray or translucent. Fine banding can preserve changes in ancient water chemistry or sediment input.

Field identification & locations

Identify it by its opaque earthy bands, waxy polish, lack of visible large crystals, and ability to scratch ordinary glass; a steel file should not easily scratch it. Common sources include sedimentary basins worldwide, especially the United States, Mexico, India, and Australia.