mineral
Polished agate/geode slice
Microcrystalline quartz (chalcedony), mainly SiO₂, with possible calcite or quartz druse
AI-generated identification · may be incorrectGray-white, translucent to opaque, waxy-to-vitreous luster, and fine concentric/botryoidal banding; quartz hardness is about 7 Mohs, with no obvious cleavage and specific gravity near 2.6. The dark outer rim may be iron/manganese-stained chalcedony or host rock.
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Physical properties
Gray-white, translucent to opaque, waxy-to-vitreous luster, and fine concentric/botryoidal banding; quartz hardness is about 7 Mohs, with no obvious cleavage and specific gravity near 2.6. The dark outer rim may be iron/manganese-stained chalcedony or host rock.
Formation & geological history
Likely silica-rich groundwater filled cavities in volcanic rock, depositing chalcedony and later quartz crystals over long periods, commonly in Cenozoic basaltic terrains. The specimen has been cut and polished, so its exact locality and age cannot be determined visually.
Uses & applications
Used as a decorative slice, lapidary display, paperweight, or jewelry component; attractive agates commonly sell as affordable collector material.
Geological facts
The pale interior resembles botryoidal chalcedony or a quartz-lined cavity rather than a clearly identifiable fossil. Acid testing can help detect calcite, while a steel file should not scratch quartz.
Field identification & locations
Look for curved/concentric bands, translucent edges, and a glassy or waxy surface; common sources include Brazil, Uruguay, Mexico, Madagascar, and the United States. Value depends heavily on color, pattern, polish, and verified provenance.
