mineral

Polished agate or jasper cabochon

Microcrystalline quartz (chalcedony), SiO₂, possibly brecciated or plume agate

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; cream, yellow, tan, and brown coloration with translucent chalcedony and darker curved banding. Typically waxy to vitreous luster, cryptocrystalline structure, no visible cleavage, and specific gravity around 2.6.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and inclusions in successive layers; the specimen is likely polished and shaped as a cabochon. Formation commonly occurred in Cenozoic or older volcanic settings, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, and ornamental objects; attractive patterned pieces have modest jewelry and collector value.

Geological facts

The internal plume- or breccia-like markings are produced by mineral inclusions and later fracturing or fluid deposition, not by large visible crystals.

Field identification & locations

Identify by its smooth polish, waxy translucency, curved or irregular chalcedony banding, and inability to scratch with a fingernail or copper coin. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.