mineral

Carnelian (Chalcedony)

SiO2 (Silicon Dioxide with Iron Oxide inclusions)

Hardness: 6.5-7 on Mohs scale. Color: Translucent reddish-orange to deep brownish-red. Luster: Waxy to vitreous. Structure: Microcrystalline/Cryptocrystalline quartz. Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Color: Translucent reddish-orange to deep brownish-red
Luster: Waxy to vitreous

Identified July 22, 2026More mineral →

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Physical properties

Formation & geological history

Forms through secondary precipitation of silica in volcanic host rocks (basalt, andesite cavities) or sedimentary gravels. Colored by trace amounts of iron oxides (goethite or hematite).

Uses & applications

Widely used for lapidary art, gemstones, beads, carved seals, and cabochons. Historically valued for signet rings as wax does not stick to it easily.

Geological facts

Carnelian has been used as a gemstone for over 4,500 years, being popular in ancient Egyptian, Roman, and Sumerian jewelry. Heating natural brownish chalcedony often enhances its red and orange hues by oxidizing the iron.

Field identification & locations

Identified by its distinctive warm translucent red-orange glow under backlighting, smooth water-worn rounded pebble texture, and high hardness (cannot be scratched by a steel nail). Commonly found in gravel beds, rivers, and beach beaches in Brazil, India, Madagascar, and Oregon (USA).

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