gemstone

Banded agate (likely fire agate or iron-stained chalcedony)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent brown, orange, cream, gray, and black bands with vitreous to waxy luster. Quartz is trigonal but occurs here as cryptocrystalline masses, commonly without visible cleavage; specific gravity is about 2.6.

Identified August 11, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony; iron oxides create the orange-brown coloration. Individual layers may form over long intervals, commonly during Cenozoic volcanic activity.

Uses & applications

Used for cabochons, carvings, beads, and polished specimens; rough pieces are popular among collectors. Ordinary material is typically inexpensive, while vivid chatoyant fire agate can be valuable.

Geological facts

The specimen appears partly weathered or naturally fractured, with white quartz/chalcedony and dark iron- or manganese-rich zones. Strong color play would support identification as fire agate, but the photograph alone cannot confirm it.

Field identification & locations

Identify by its very hard, silica-rich texture, curved banding, waxy surface, and resistance to scratching by steel; glass should not scratch it. Common sources include Arizona and Mexico, plus volcanic regions worldwide.