sedimentary

Polished brecciated jasper

Microcrystalline quartz (chalcedony), commonly SiO₂, with iron-oxide and other mineral fragments

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, opaque, fine-grained, and waxy to vitreous-lustrous; brown, gray, black, and rusty-red coloration reflects iron oxides and brecciation. No visible cleavage; specific gravity is about 2.5–2.7.

Identified August 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater cements fractured volcanic or sedimentary rock fragments, often during low-temperature hydrothermal alteration; exact age and locality cannot be determined from the photograph. The specimen has been shaped and polished.

Uses & applications

Used for cabochons, beads, carvings, worry stones, and decorative objects; occasionally as ornamental stone. Common polished pieces generally have modest collector value.

Geological facts

The angular contrasting patches and rusty vein-like zones are characteristic of brecciated jasper rather than uniform jasper or agate. Its appearance can overlap with brecciated rhyolite and other silicified rocks.

Field identification & locations

Identify it by its opaque, very fine-grained texture, conchoidal fracture, hardness, and iron-rich color patterns; it should resist scratching by a steel knife. Common sources include India, Madagascar, Brazil, Mexico, and the western United States.