mineral

Polished banded agate

Microcrystalline quartz (chalcedony), SiO₂

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; brown, cream, and gray bands with a waxy to vitreous polish. Trigonal quartz in microscopic fibers; no cleavage, conchoidal fracture, specific gravity about 2.6.

Identified September 23, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; brown, cream, and gray bands with a waxy to vitreous polish. Trigonal quartz in microscopic fibers; no cleavage, conchoidal fracture, specific gravity about 2.6.

Formation & geological history

Silica-rich fluids deposited successive chalcedony layers in a cavity, commonly in volcanic rock. Agate occurs in rocks of many ages; the image does not reveal a precise age or locality.

Uses & applications

Used for beads, cabochons, ornaments, and small carvings; also collected as a polished specimen.

Geological facts

Agate’s bands record changing conditions during silica deposition, and some varieties display striking fortification or eye-like patterns.

Field identification & locations

Identify by its fine-grained texture, hardness, and distinct curved or parallel bands; common sources include Brazil, Uruguay, India, and the western United States. A typical polished palm-sized piece is roughly $5–$30 USD.