gemstone
Carnelian (Polished Agate)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on the Mohs scale. Color: Translucent reddish-orange to deep orange-red. Luster: Vitreous to waxy. Crystal structure: Trigonal (microcrystalline/cryptocrystalline quartz). Cleavage: None, exhibits conchoidal fracture.
- Hardness
- 6
- Color
- Translucent reddish-orange to deep orange-red
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 on the Mohs scale. Color: Translucent reddish-orange to deep orange-red. Luster: Vitreous to waxy. Crystal structure: Trigonal (microcrystalline/cryptocrystalline quartz). Cleavage: None, exhibits conchoidal fracture.
Formation & geological history
Forms at low temperatures in cavities of volcanic rocks (basalts and andesites) through silica-rich fluid deposition. Iron oxide impurities (hematite) impart the characteristic reddish-orange color.
Uses & applications
Used widely in jewelry (beads, cabochons, rings), decorative carvings, lapidary art, and as a popular tumbled gemstone for collectors.
Geological facts
Carnelian has been used in jewelry making for over 4,500 years. Ancient Romans used carnelian to create engraved signet rings for sealing documents, as hot wax does not stick to it.
Field identification & locations
Identified by its rich translucent orange-red hue, waxy finish, and smooth tumbled surface. Common in gravel deposits, riverbeds, and volcanic regions worldwide including the Western US.
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