gemstone

Polished carnelian agate (likely dyed or heat-treated)

Microcrystalline quartz, chiefly chalcedony; SiO₂

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent honey-orange to reddish-brown, with vitreous/waxy luster and no visible cleavage. The smooth cabochon/tumbled form obscures its typical fibrous chalcedony structure; internal clouding may indicate agate banding.

Identified August 20, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills vesicles in volcanic rocks, commonly during the Cenozoic and older volcanic episodes. Iron impurities create the orange-brown color, sometimes enhanced by heating or dyeing.

Uses & applications

Used for cabochons, beads, carvings, and inexpensive jewelry; also collected as a polished decorative stone. Typical value is modest unless strongly banded, naturally vivid, or unusually large.

Geological facts

Carnelian is the reddish-orange variety of chalcedony, while agate generally shows banding or patterned zones. A glass-like appearance and perfectly uniform color can suggest imitation glass, but this specimen appears consistent with polished chalcedony.

Field identification & locations

Common sources include Brazil, Uruguay, India, Madagascar, Botswana, and the United States. Field identification relies on hardness—quartz should scratch glass—plus curved fracture, translucency, and absence of cleavage; confirm with magnification or gem testing.