mineral
Polished agate slice
Agate, a banded variety of chalcedony (microcrystalline SiO₂)
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; translucent gray, cream, and white concentric bands with a waxy-to-glassy polish. Microcrystalline quartz; no distinct cleavage, conchoidal fracture; specific gravity about 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; translucent gray, cream, and white concentric bands with a waxy-to-glassy polish. Microcrystalline quartz; no distinct cleavage, conchoidal fracture; specific gravity about 2.6.
Formation & geological history
Silica-rich fluids deposited successive chalcedony layers in a cavity, commonly in volcanic rock; the slice is cut and polished. Agates form across many geological ages, so the specimen’s age and locality cannot be determined from the image.
Uses & applications
Used for jewelry, ornaments, bookends, and decorative slabs; also collected for its banding.
Geological facts
The central bands record successive mineral deposition and can outline the former cavity, or geode, interior.
Field identification & locations
Look for curved, nested bands and a fine-grained, translucent appearance; agate occurs worldwide, especially in volcanic regions and river gravels. A common polished slice like this typically sells for about $5–$30 USD, depending on size, pattern, and workmanship.
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