gemstone

Tumbled red-brown stone, possibly carnelian

Likely chalcedony (microcrystalline quartz, SiO₂); identification from the image is uncertain

AI-generated identification · may be incorrect

Smooth, polished, translucent-to-opaque reddish brown with a vitreous to waxy luster; quartz hardness is 7 Mohs, with no visible cleavage and a conchoidal fracture when broken. Crystal structure is trigonal at the quartz level, though chalcedony is too fine-grained to show visible crystals.

Identified September 27, 2026More gemstone →

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Physical properties

Formation & geological history

If carnelian, it formed as iron-colored chalcedony in silica-rich cavities or veins, often in volcanic rocks; deposits occur across many geological ages. Tumbling is human processing and does not alter its geological origin.

Uses & applications

Used for beads, cabochons, carvings, and inexpensive jewelry or decorative pieces.

Geological facts

Carnelian is a reddish variety of chalcedony, colored chiefly by iron impurities; similar-looking glass and other stones are common substitutes.

Field identification & locations

Check for natural color variation and conchoidal fracture; a hardness test or magnification can help distinguish it from glass, but the pictured polished stone cannot be identified confidently. Carnelian occurs worldwide, including India, Brazil, and Uruguay.