mineral
Polished agate slab (likely moss or plume agate)
Microcrystalline quartz, SiO₂; chalcedony with possible iron-oxide inclusions
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; pale gray-white with brown-gray inclusions and a polished surface. Quartz has trigonal crystal structure, but chalcedony is too fine-grained to show visible crystals; agate typically has no distinct cleavage and a vitreous to waxy luster.
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Physical properties
Hardness 6.5–7 Mohs; pale gray-white with brown-gray inclusions and a polished surface. Quartz has trigonal crystal structure, but chalcedony is too fine-grained to show visible crystals; agate typically has no distinct cleavage and a vitreous to waxy luster.
Formation & geological history
Forms as silica-rich fluids fill cavities and fractures, depositing layered chalcedony; inclusions create plume-like patterns. Agates occur in rocks of many ages, commonly in volcanic settings.
Uses & applications
Used for decorative slabs, jewelry, carvings, and lapidary collecting.
Geological facts
Agate is a banded or patterned variety of chalcedony; this image’s subdued pattern may be better identified from close-up detail.
Field identification & locations
Look for waxy luster, hardness sufficient to scratch glass, and fine translucent chalcedony; common sources include Brazil, Uruguay, India, and the western United States. A photograph cannot confirm the exact agate variety.
