mineral
Likely tumbled brown agate
Microcrystalline quartz (SiO₂), commonly chalcedony; exact identification is uncertain from the image
AI-generated identification · may be incorrectSmall, smooth, polished brown specimen with dark and amber tones and a vitreous-to-waxy luster. If agate/chalcedony, Mohs hardness is about 6.5–7, with no visible cleavage and a trigonal quartz structure.
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Physical properties
Small, smooth, polished brown specimen with dark and amber tones and a vitreous-to-waxy luster. If agate/chalcedony, Mohs hardness is about 6.5–7, with no visible cleavage and a trigonal quartz structure.
Formation & geological history
Agate forms as silica-rich water deposits chalcedony in cavities, often in volcanic rocks; its age depends on the host deposit and can range from millions to hundreds of millions of years.
Uses & applications
Tumbled agates are used in jewelry, ornaments, and mineral collections; industrial chalcedony is a minor source of silica.
Geological facts
Agate is a banded variety of chalcedony, though banding is not clearly visible on this small specimen.
Field identification & locations
Look for hardness near 7, a waxy luster, and translucent edges; a scratch test or closer inspection could distinguish agate from other polished brown minerals. Agates occur worldwide, notably in Brazil, Uruguay, India, and the United States.
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