sedimentary

Red jasper / red chert

Microcrystalline quartz (chalcedony), SiO₂, colored chiefly by iron oxides

AI-generated identification · may be incorrect

Typically Mohs 6.5–7, opaque to slightly translucent, dark red to mahogany, with a dull-to-waxy luster and conchoidal fracture; no visible cleavage. The specimen appears naturally fractured or roughly knapped, with possible iron staining and minor quartz/chalcedony variation.

Identified September 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids or sediment cement into microcrystalline quartz, with hematite or related iron minerals producing the red color; deposits range from Precambrian to much younger. It commonly occurs in volcanic or sedimentary iron- and silica-rich settings.

Uses & applications

Used for carvings, cabochons, beads, tumbled stones, decorative objects, and historically as an abrading or tool material. Common rough pieces generally have modest commercial value.

Geological facts

Red jasper is a variety of opaque chalcedony rather than a separate mineral species; “chert” is the broader geological texture-based term. Strong conchoidal fracture and red iron coloration are characteristic.

Field identification & locations

Look for a dense, opaque red body, waxy surface, very hard edges, and inability to scratch it with a steel knife; it should scratch glass, unlike most red glass or resin. Common sources include India, Madagascar, Brazil, the United States, and Australia.