Rock Identifier
Chalcedony with jasper (likely brecciated jasper) (Microcrystalline quartz, SiO₂, with iron-oxide-rich jasper fragments) — mineral
mineral

Chalcedony with jasper (likely brecciated jasper)

Microcrystalline quartz, SiO₂, with iron-oxide-rich jasper fragments

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque to translucent reddish-brown, cream, and gray; waxy to dull luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The specimen appears naturally rough or lightly worked, with rusty iron-oxide coloration.

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Physical properties

Hardness about 6.5–7 Mohs; opaque to translucent reddish-brown, cream, and gray; waxy to dull luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The specimen appears naturally rough or lightly worked, with rusty iron-oxide coloration.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, later incorporating or cementing iron-stained fragments; commonly associated with volcanic terrains and hydrothermal activity. Individual deposits may range from Paleozoic to Cenozoic in age.

Uses & applications

Used for cabochons, carvings, beads, ornaments, and lapidary slabs; lower-grade material is decorative stone. Collector value is primarily based on color, pattern, translucency, and polishability.

Geological facts

Jasper is an opaque variety of chalcedony, while translucent zones are chalcedonic quartz; the boundary between jasper and agate is often gradual.

Field identification & locations

Look for very fine grain, waxy surfaces, conchoidal breaks, and inability to scratch with a steel knife; quartz should scratch glass. Common localities include Oregon, California, Arizona, Brazil, Madagascar, and Australia.