mineral
Carnelian (Chalcedony)
Silicon Dioxide (SiO2) - variety of Chalcedony
Hardness: 6.5-7 on Mohs scale; Color: Reddish-orange, amber, or brownish-red; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal.
- Hardness
- 6
- Color
- Reddish-orange, amber, or brownish-red
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-orange, amber, or brownish-red; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal.
Formation & geological history
Formed as a result of silica-rich groundwater percolating through cavities in volcanic rocks. The orange-red color is caused by iron oxide impurities. It is found in igneous environments and often weathered into sedimentary deposits.
Uses & applications
Commonly used in jewelry (cabochons, beads, rings), decorative carvings, and as a popular lapidary material for hobbyists.
Geological facts
Carnelian was highly valued in ancient Egypt, where it was believed to assist the soul's journey into the afterlife. It was also widely used for signet rings and cylinder seals because hot wax does not stick to it.
Field identification & locations
Identify by its translucent waxy luster and shell-like (conchoidal) fractures. Found in riverbeds, gravel deposits, and volcanic field areas in Brazil, India, Madagascar, and the United States (especially the Pacific Northwest).
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sedimentary
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Metamorphic
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
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Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous