mineral
Likely tumbled brown agate
Microcrystalline quartz (SiO₂), variety chalcedony; identification is tentative from the image
AI-generated identification · may be incorrectOpaque to translucent brown, with a waxy-to-dull luster and possible dark banding. Quartz hardness is about 7 Mohs; the specimen appears rounded and polished, obscuring natural fracture and crystal form.
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Physical properties
Opaque to translucent brown, with a waxy-to-dull luster and possible dark banding. Quartz hardness is about 7 Mohs; the specimen appears rounded and polished, obscuring natural fracture and crystal form.
Formation & geological history
Agate forms as silica-rich fluids deposit chalcedony in cavities, commonly in volcanic rocks; the specimen’s age and source cannot be determined visually.
Uses & applications
Used for jewelry, decorative objects, and lapidary collecting; agate is also used in some precision and ornamental applications.
Geological facts
Agate is a banded variety of chalcedony, though banding may be subtle or absent in small tumbled pieces.
Field identification & locations
Look for curved or concentric bands and a waxy luster; a fresh cut or strong backlighting can reveal internal structure. Agates occur worldwide, including Brazil, Uruguay, India, and the United States.
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