mineral

Polished agate/jasper pebble

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray, cream, brown, and translucent zones with a waxy to vitreous luster. Massive, cryptocrystalline structure; no visible cleavage, conchoidal fracture, and high polishability.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater filled cavities or fractures in volcanic rock, later incorporating iron-rich impurities and becoming chalcedony or jasper. Such material commonly formed during the Cenozoic or older volcanic episodes, though the specimen’s age cannot be determined visually.

Uses & applications

Used for cabochons, beads, carvings, tumbled stones, and ornamental objects; attractive polished pieces are popular with collectors.

Geological facts

The opaque portions are jasper-like, while translucent areas are agate-like; both are varieties of microcrystalline quartz and may occur together.

Field identification & locations

Identify by its glassy/waxy polish, great toughness, mixed translucent and opaque silica zones, and lack of obvious cleavage; common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States. The image appears to show a shaped or tumbled commercial specimen.