sedimentary

Tumbled jasper/chert pebble

Microcrystalline quartz (SiO₂), likely jasper or silicified chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray, brown, reddish, and cream mottling with a dull-to-waxy luster. Dense, opaque, cryptocrystalline quartz with no visible cleavage; typical specific gravity is 2.เน6–2.7.

Identified August 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids replaced or cemented sediment, producing microcrystalline quartz; the exact geological age cannot be determined from the photograph. Natural weathering and tumbling rounded the pebble, likely enhanced by human polishing.

Uses & applications

Used as an inexpensive lapidary material for cabochons, beads, carvings, and decorative stones; it has little industrial value in this small form.

Geological facts

Jasper and chert are varieties of opaque microcrystalline quartz, and their colors commonly result from iron oxides and other trace minerals.

Field identification & locations

Identify it by its very hard, nonmetallic, waxy surface, opaque mottled pattern, and inability to scratch with a steel knife; a streak or hardness test can distinguish it from softer look-alikes. Common in gravel beds, river deposits, and silica-rich sedimentary terrains worldwide.