mineral
Polished agate (likely chalcedony)
Microcrystalline quartz, SiO₂; agate is banded chalcedony
AI-generated identification · may be incorrectOpaque to translucent gray-white with rusty brown inclusions or bands and a waxy-to-glassy polish. Quartz hardness is 6.5–7 Mohs; trigonal crystal structure, no cleavage, and specific gravity about 2.6.
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Physical properties
Opaque to translucent gray-white with rusty brown inclusions or bands and a waxy-to-glassy polish. Quartz hardness is 6.5–7 Mohs; trigonal crystal structure, no cleavage, and specific gravity about 2.6.
Formation & geological history
Silica-rich fluids deposited microcrystalline quartz in cavities or fractures, commonly in volcanic rocks; iron oxides produce the brown coloration. The specimen’s age and locality cannot be determined from the image.
Uses & applications
Used for beads, cabochons, ornaments, and lapidary collecting; agate is also used in some precision and decorative applications.
Geological facts
Agate is a variety of chalcedony, and its patterns form through successive silica deposition. The pictured piece appears rounded and polished.
Field identification & locations
Look for waxy luster, hardness sufficient to scratch glass, and curved or irregular color bands; common sources include Brazil, Uruguay, India, and the United States. Exact identification and origin need closer inspection.
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