mineral

Banded agate (likely jasper–quartz agate)

Microcrystalline quartz, SiO₂, with iron-oxide and other mineral impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; opaque brown, white, gray, and reddish-orange bands; waxy to vitreous luster; cryptocrystalline quartz with no cleavage and conchoidal fracture. The rounded form appears naturally weathered or possibly tumbled.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, depositing successive layers of chalcedony and quartz; coloration commonly comes from iron oxides. Individual agate layers may form over thousands to millions of years, typically in volcanic terrains.

Uses & applications

Used for cabochons, beads, carvings, bookends, and decorative stone; polished pieces are popular collectibles, while crushed agate is used in abrasives and laboratory mortars.

Geological facts

The specimen appears to include a porous white quartz/chalcedony zone beneath darker jasper-like material. Agate banding records changing chemistry during repeated silica deposition.

Field identification & locations

Identify by hardness, fine banding, waxy luster, lack of cleavage, and resistance to scratching by a steel blade; common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Exact locality requires testing or provenance.