sedimentary

Polished banded chert or jasper pebble

Microcrystalline quartz (SiO₂), likely banded chert; exact variety uncertain from the image

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent gray-brown with tan and cream wavy bands, waxy to subvitreous luster, and no obvious cleavage. Dense, fine-grained, cryptocrystalline quartz; specific gravity approximately 2.6.

Identified September 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater or marine silica lithified into microcrystalline quartz, with layered impurities producing the banding; commonly Paleozoic to Cenozoic, depending on source. The rounded shape reflects prolonged stream or beach abrasion.

Uses & applications

Used as decorative stone, tumbled material, cabochons, and occasionally knappable toolstone; generally not significant for construction in pebble form.

Geological facts

The specimen may also be silicified wood or finely banded agate, since the visible parallel structure resembles replacement textures. A steel file should not easily scratch it, while quartz should.

Field identification & locations

Common in gravel beaches and river deposits worldwide, especially areas draining chert-bearing sedimentary formations. Confirm with a hardness test, streak (white), and close inspection for fibrous wood grain or translucent agate banding.