sedimentary

Polished brown chert or jasper pebble

Microcrystalline quartz (SiO₂), likely chert/jasper with iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown to reddish-brown, opaque, and waxy to dull-lustrous with a smooth tumbled surface. It is cryptocrystalline quartz, has no visible cleavage, and typically breaks with a conchoidal fracture; white patches may be quartz, carbonate, or weathering residue.

Identified September 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or cements sediment, commonly in limestone, volcanic, or marine settings; iron oxides create the brown coloration. Its precise geological age cannot be determined from the photograph and may range from Paleozoic to recent gravel deposits.

Uses & applications

Used as a durable aggregate, decorative stone, lapidary material, and occasionally for cabochons or carvings. This small tumbled specimen has modest commercial value.

Geological facts

Chert and jasper are field terms for dense microcrystalline quartz; jasper is generally more opaque and impurity-rich. The rounded shape indicates transport or deliberate tumbling/polishing.

Field identification & locations

Test for glass-scratching hardness and inspect a fresh edge for a smooth, glassy conchoidal fracture; it should not fizz strongly in dilute acid unless carbonate-rich. Common in river gravels and sedimentary formations worldwide.