sedimentary

Tumbled jasper/chert pebble

Microcrystalline quartz (SiO₂), likely iron-stained jasper or chert

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque reddish-brown to tan, with a dull-to-waxy luster and very fine-grained, cryptocrystalline structure. No visible cleavage; conchoidal fracture is typical, though the specimen is rounded and polished by abrasion.

Identified August 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater replaces or fills sediments, producing dense microcrystalline quartz; iron oxides create the brown-red color. The exact geological age and locality cannot be determined from the photograph.

Uses & applications

Used as a decorative stone, cabochon, bead, or lapidary material; small tumbled pieces commonly sell as curios or specimens.

Geological facts

Jasper is an opaque variety of chalcedony, while chert is the broader rock term for dense microcrystalline quartz. Color zoning and iron staining are common identification clues.

Field identification & locations

Test hardness against glass or a steel file, inspect for a waxy texture and conchoidal edges, and use a streak or specific-gravity test if needed. Common worldwide, especially in silica-rich sedimentary and volcanic terrains.