mineral

Likely fire agate

Botryoidal chalcedony (microcrystalline SiO₂) with iron-oxide layers

AI-generated identification · may be incorrect

Brown-gray, irregular rough piece with orange-red patches; quartz hardness 6.5–7, vitreous to waxy luster, cryptocrystalline structure, no visible cleavage. The image alone cannot confirm the characteristic iridescent play of color that distinguishes fire agate.

Identified October 13, 2026More mineral →

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Physical properties

Formation & geological history

Forms as silica fills cavities in volcanic rocks, with iron-oxide layers producing color; notable deposits are generally Cenozoic in age, especially in the southwestern United States and Mexico.

Uses & applications

Iridescent material is cut and polished for jewelry and collecting; non-iridescent pieces have modest decorative value.

Geological facts

Fire agate is a variety of chalcedony, not a separate mineral species; its shifting colors come from thin internal layers.

Field identification & locations

Look for rounded, botryoidal surfaces and, on a polished face, vivid shifting red, orange, or green flashes. Similar-looking iron-stained chalcedony can lack fire, so identification needs closer inspection.