mineral

Polished banded agate (likely Botswana or fortification agate)

Microcrystalline quartz, SiO₂, chiefly chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-white, tan, and brown bands with a vitreous to waxy polish. Quartz is trigonal microscopically and has no cleavage; specific gravity is about 2.6.

Identified August 24, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; translucent gray-white, tan, and brown bands with a vitreous to waxy polish. Quartz is trigonal microscopically and has no cleavage; specific gravity is about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in successive layers; banding records changing fluids and impurities. Individual agate nodules commonly formed during the Cenozoic or older volcanic episodes.

Uses & applications

Used for cabochons, carvings, beads, bookends, and ornamental objects; it has modest jewelry and collector value.

Geological facts

The curved, concentric layering and translucency are characteristic of agate, while brown coloration commonly reflects iron oxides. The piece appears cut and polished, possibly shaped as a small carving or pendant.

Field identification & locations

Identify it by curved parallel bands, waxy translucency, glassy polish, and lack of obvious cleavage; a steel file should not easily scratch it. Common sources include Brazil, Uruguay, Botswana, Mexico, India, and the United States.