mineral
Banded agate (rough or partly polished)
Agate, a microcrystalline variety of quartz (SiO₂; chalcedony)
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent gray-brown with curved bands and a waxy-to-glassy luster. Quartz crystals are microscopic and the specimen has no obvious cleavage; specific gravity is about 2.6.
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Physical properties
Hardness 6.5–7 Mohs; translucent gray-brown with curved bands and a waxy-to-glassy luster. Quartz crystals are microscopic and the specimen has no obvious cleavage; specific gravity is about 2.6.
Formation & geological history
Silica-rich fluids deposited successive chalcedony layers in a cavity, commonly in volcanic rock. Agates form across many geological ages; the image alone cannot establish this specimen’s age.
Uses & applications
Used for jewelry, carvings, ornaments, and lapidary collecting; its toughness and banding make it suitable for cutting and polishing.
Geological facts
Agate’s banding records changes in silica deposition and fluid conditions during cavity filling.
Field identification & locations
Look for translucent chalcedony with curved or concentric bands and a hardness sufficient to scratch glass. Agates occur worldwide, especially in volcanic regions; this specimen’s locality is unknown.
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