gemstone

Fire Agate

Silicon Dioxide (SiO2 with iron oxide inclusions)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Translucent brown/orange with iridescent fiery flash (red, gold, orange); Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/Trigonal; Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Luster: Waxy to vitreous

Identified July 22, 2026More gemstone →

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Physical properties

Formation & geological history

Formed during volcanic activity in the Tertiary period, where hot water rich in silica and iron oxide filled bubbles and cracks within surrounding rock, depositing thin layers of chalcedony and goethite/limonite.

Uses & applications

Used primarily in jewelry making, wire-wrapping, cabochons, and as a popular semi-precious collector's specimen.

Geological facts

The fiery iridescent colors inside fire agate are caused by the Schiller effect, a light interference phenomenon produced by thin, alternating layers of silica and iron oxide (goethite).

Field identification & locations

Identified by its distinctive botryoidal structure and internal fiery shimmer when backlit or turned under light. Commonly found in Southwestern USA (Arizona, California) and Northern Mexico.