mineral
Carnelian / Chalcedony
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Orange, reddish-brown, honey-yellow; Luster: Waxy to vitreous; Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal; Translucent to semi-opaque.
- Hardness
- 6
- Color
- Orange, reddish-brown, honey-yellow
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Orange, reddish-brown, honey-yellow; Luster: Waxy to vitreous; Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal; Translucent to semi-opaque.
Formation & geological history
Formed by the deposition of silica-rich groundwater in cavities of igneous and sedimentary rocks. The orange coloration is caused by iron oxide (limonite or hematite) impurities. Often found as water-worn pebbles in river beds.
Uses & applications
Extensively used in lapidary work, jewelry (beads, cabochons, carved seals), and as a collector's mineral. Industrially used for its hardness in abrasive applications.
Geological facts
Carnelian was prized by ancient Romans and Greeks for signet rings because hot wax does not stick to it. It has been used for beads since the Neolithic period over 5,000 years ago.
Field identification & locations
Identified by its waxy luster, translucency, and inability to be scratched by a steel knife. Frequently found in river gravel or beach wash, particularly in basaltic regions.
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Mineral
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Mineral/Rock
Granite
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igneous