mineral
Tumbled brown agate (likely carnelian/chalcedony)
Microcrystalline quartz, SiO₂; chalcedony, possibly iron-stained
AI-generated identification · may be incorrectBrown to reddish-brown, translucent in places, with a waxy-to-glassy luster; quartz crystal structure is too fine-grained to see. Mohs hardness 6.5–7; no obvious cleavage, conchoidal fracture; specific gravity about 2.6.
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Physical properties
Brown to reddish-brown, translucent in places, with a waxy-to-glassy luster; quartz crystal structure is too fine-grained to see. Mohs hardness 6.5–7; no obvious cleavage, conchoidal fracture; specific gravity about 2.6.
Formation & geological history
Silica-rich fluids deposited chalcedony in cavities or veins, later colored by iron oxides; the specimen appears mechanically tumbled and polished. Such deposits formed in many geological settings and ages.
Uses & applications
Used for beads, cabochons, carvings, and decorative collections; this small piece is mainly a craft or collector specimen.
Geological facts
Agate is a banded variety of chalcedony, though banding is not clearly visible in this photo.
Field identification & locations
The rounded, glossy surface suggests a tumbled quartz-family stone; hardness and conchoidal fracture help distinguish it from softer lookalikes. Agates occur worldwide, including Brazil, Uruguay, India, and the United States.
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