mineral
Tumbled agate (likely iron-stained chalcedony)
Microcrystalline quartz, SiO₂; agate is banded chalcedony
AI-generated identification · may be incorrectTypically Mohs 6.5–7, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. This small rounded specimen is mottled brown and gray; distinct banding is not evident in the image.
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Physical properties
Typically Mohs 6.5–7, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. This small rounded specimen is mottled brown and gray; distinct banding is not evident in the image.
Formation & geological history
Agate forms as silica-rich fluids fill cavities in volcanic rocks, with layers deposited over time. Its age depends on the host rock and locality; the specimen’s origin cannot be determined from appearance alone.
Uses & applications
Commonly tumbled for collecting, crafts, and jewelry; agate is also used for ornamental objects and, historically, precision components.
Geological facts
Iron oxides commonly produce brown, rust-colored patches in chalcedony.
Field identification & locations
Look for waxy luster, hardness near 7, and translucent edges; agate commonly occurs in volcanic cavities and stream gravels. The image does not show diagnostic bands, so identification is tentative.
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