Rock Identifier
Polished red jasper (likely brecciated jasper) (Jasper, microcrystalline quartz/chalcedony (SiO₂), colored mainly by iron oxides) — mineral
mineral

Polished red jasper (likely brecciated jasper)

Jasper, microcrystalline quartz/chalcedony (SiO₂), colored mainly by iron oxides

AI-generated identification · may be incorrect

Opaque, reddish-brown and black, with a polished vitreous-to-waxy luster and irregular brecciated pattern. Quartz hardness is about 6.5–7 Mohs; no visible cleavage; specific gravity about 2.5–2.7.

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Physical properties

Opaque, reddish-brown and black, with a polished vitreous-to-waxy luster and irregular brecciated pattern. Quartz hardness is about 6.5–7 Mohs; no visible cleavage; specific gravity about 2.5–2.7.

Formation & geological history

Forms when silica-rich groundwater replaces or cements volcanic ash, sediment, or rock fragments, with iron producing the red coloration. Jasper deposits range from Precambrian to recent geological ages.

Uses & applications

Used for cabochons, beads, carvings, tumbled stones, and ornamental objects; occasionally used as a decorative facing stone. Common polished specimens typically have modest value.

Geological facts

Jasper is a variety of opaque chalcedony and may contain hematite, goethite, magnetite, or volcanic fragments. The pictured specimen appears water-worn or tumbled and polished rather than raw.

Field identification & locations

Identify it by its opacity, strong red-brown iron staining, hardness, and lack of cleavage; it should not scratch easily with a steel knife. Common sources include the western United States, Madagascar, Brazil, India, and Australia.