gemstone

Polished carnelian/chalcedony

Carnelian, a red-orange variety of cryptocrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent orange-red to brown with a waxy-to-glassy luster and no visible cleavage. The elongated polished piece shows banding or included darker brown material, consistent with chalcedony or agate rather than a uniform crystal.

Identified September 15, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, with iron impurities producing the red-orange color; commonly Cenozoic to older volcanic-hosted deposits. Typical sources include India, Brazil, Uruguay, Madagascar, and the United States.

Uses & applications

Used for beads, cabochons, carvings, seals, and ornamental objects; durable enough for jewelry and decorative stonework.

Geological facts

Carnelian is colored mainly by iron oxides and may deepen in color with heating. It is a microcrystalline quartz aggregate, so individual quartz crystals are generally invisible.

Field identification & locations

Identify it by its orange-red translucency, waxy luster, high hardness, and lack of cleavage; it should resist scratching by a steel knife, though testing may damage the polish. The dark edge may indicate agate banding or a natural matrix inclusion.