gemstone

Polished carnelian agate

Microcrystalline quartz (chalcedony), SiO₂, iron-oxide colored

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent reddish-orange to brown with gray/olive chalcedony, waxy to vitreous luster, cryptocrystalline structure, and no visible cleavage. The glossy surface indicates polishing, possibly with natural botryoidal or banded textures.

Identified August 30, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock; iron oxides create the red-orange coloration. Most specimens are Cenozoic to older, with major sources in Brazil, Uruguay, India, Madagascar, and the United States.

Uses & applications

Used for cabochons, beads, carvings, seals, and ornamental objects; durable enough for jewelry and lapidary work.

Geological facts

Carnelian is the red-orange variety of chalcedony, while agate typically shows banding or contrasting chalcedony zones. Color may deepen after gentle heating, which enhances iron-oxide tones.

Field identification & locations

Identify by its waxy luster, translucency, lack of cleavage, hardness, and red zones that often glow at the edges; glass is usually more uniformly transparent and may show bubbles. Exact variety is difficult to confirm from one photograph.