gemstone

Polished agate/chalcedony fragment (probable)

Microcrystalline quartz, SiO₂; chalcedony with possible iron-oxide banding

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent gray-brown with reddish bands, vitreous to waxy luster, cryptocrystalline structure, and no obvious cleavage. The image is too blurred for confident variety-level identification.

Identified August 15, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in successive bands; ages range from Paleozoic to recent depending on locality. This appears cut or naturally worn and polished rather than a fresh crystal.

Uses & applications

Used for cabochons, beads, carvings, tumbling, and ornamental objects; agate is also collected as a lapidary material. It has little industrial use beyond silica-bearing stone products.

Geological facts

Agate banding records changing chemistry, temperature, and fluid flow during cavity filling. Red coloration commonly comes from hematite or other iron oxides.

Field identification & locations

Common in volcanic terrains and gravel deposits worldwide, especially Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Confirm with a hardness test against glass, waxy translucence, and curved or parallel banding; avoid testing valuable pieces.