sedimentary

Banded chert or jasper pebble

Microcrystalline quartz (SiO₂), commonly with iron-oxide and clay impurities

AI-generated identification · may be incorrect

Typically 6.5–7 Mohs; opaque yellow-tan with dark gray/black wispy bands, dull to waxy luster, and no visible cleavage. Dense, fine-grained cryptocrystalline quartz; the smoothly rounded shape indicates water abrasion or tumbling.

Identified August 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids replaced or cemented sediment, with iron- and manganese-rich layers producing the banding; age depends on source bedrock, commonly Precambrian to Paleozoic. The specimen was probably collected from a stream, beach, or gravel deposit.

Uses & applications

Used as a lapidary material for cabochons, carvings, beads, and decorative stones; attractive pieces have modest collector value.

Geological facts

Chert and jasper are varieties of microcrystalline quartz, distinguished mainly by color and opacity rather than sharply separate mineral chemistry.

Field identification & locations

Identify by its very fine texture, high hardness, conchoidal fracture, and inability to scratch with a steel nail; a streak test is usually white to pale. Common worldwide, especially in ancient sedimentary formations and river gravels.