Rock Identifier
Polished jasper pebble (Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide inclusions) — mineral
mineral

Polished jasper pebble

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque cream, tan, reddish-brown, and maroon patterning; dull to waxy luster and no visible cleavage. The rounded shape indicates tumbling or natural water wear; exact variety cannot be confirmed from one photo.

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Physical properties

Hardness about 6.5–7 Mohs; opaque cream, tan, reddish-brown, and maroon patterning; dull to waxy luster and no visible cleavage. The rounded shape indicates tumbling or natural water wear; exact variety cannot be confirmed from one photo.

Formation & geological history

Jasper forms when silica-rich groundwater replaces or cements volcanic ash, sediments, or older rock, with iron oxides producing red-brown colors. Formation ages vary widely, from Precambrian to relatively young deposits.

Uses & applications

Used for cabochons, beads, carvings, decorative stones, and inexpensive collector specimens; polished pieces commonly sell for a few dollars.

Geological facts

Jasper is an opaque variety of chalcedony rather than a single mineral species, and its patterns are often unique to a locality.

Field identification & locations

Identify it by its opaque appearance, fine-grained texture, mottled iron-stained colors, and lack of cleavage; it should scratch glass but not be scratched by a steel blade. Common sources include Oregon, California, Idaho, India, Madagascar, Brazil, and Australia.