sedimentary
Polished agate slab
Banded chalcedony, a microcrystalline variety of quartz (SiO₂)
AI-generated identification · may be incorrectMostly white to cream chalcedony with subtle tan and gray banding and a polished luster; quartz hardness is 6.5–7 Mohs, with a trigonal crystal structure at the microscopic scale. The cut face shows translucent areas and curved bands along its edge.
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Physical properties
Mostly white to cream chalcedony with subtle tan and gray banding and a polished luster; quartz hardness is 6.5–7 Mohs, with a trigonal crystal structure at the microscopic scale. The cut face shows translucent areas and curved bands along its edge.
Formation & geological history
Agate forms as silica-rich fluids fill cavities in volcanic rock, depositing chalcedony in layers. The slab’s precise geological age and locality cannot be determined from the image.
Uses & applications
Polished slabs are used for display, lapidary work, and jewelry; agate is also used for ornaments and small decorative objects.
Geological facts
Agate’s bands are best seen in cross-section; polishing reveals patterns that may be faint or hidden on the rough exterior.
Field identification & locations
Identify by its waxy-to-glassy polish, translucence, and layered chalcedony bands; agate occurs worldwide, commonly in volcanic rocks. This appears to be a decorative cut specimen rather than an intact natural surface.
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