mineral

Polished banded agate nodule

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

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; cream, honey-yellow, orange, and brown concentric/translucent bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony and quartz, often colored by iron oxides. Individual agates may range from Paleozoic to Cenozoic in age depending on locality.

Uses & applications

Commonly cut and polished for ornaments, cabochons, beads, bookends, and display specimens; durable but generally modestly priced.

Geological facts

The specimen appears to be a cut or naturally smoothed nodule showing curved internal banding and iron staining, characteristic of agate rather than marble or glass.

Field identification & locations

Identify by translucent edges, curved bands, waxy surface, and conchoidal fracture; common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. A specific locality requires testing or provenance.