sedimentary

Polished brown jasper or chert pebble

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, tan, and dark gray mottling with a glassy-to-waxy polish. Massive, non-cleaving, fine-grained cryptocrystalline quartz; typical specific gravity is 2.6–2.7.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids or sediments cemented and replaced material in marine, volcanic, or hydrothermal settings; iron oxides produced the brown coloration. The specimen’s exact geological age and locality cannot be determined from the image.

Uses & applications

Used as decorative stone, cabochons, beads, bookends, and lapidary carvings; attractive polished pieces have modest collector value.

Geological facts

Jasper is an opaque variety of chalcedony, while chert is the broader fine-grained silica category; the boundary between them is often informal.

Field identification & locations

Identify it by its opaque appearance, fine texture, strong polish, lack of visible crystals, and inability to scratch with a steel knife if unweathered. Common sources include the western United States, Mexico, Brazil, India, and Australia.