mineral
Chalcedony (Carnelian variety)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to orange-brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Reddish-brown to orange-brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to orange-brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64
Formation & geological history
Forms in volcanic rocks where silica-rich fluids fill cavities (amygdales) or through low-temperature deposition in sedimentary environments. Common in post-Cretaceous basaltic flows.
Uses & applications
Used primarily in lapidary work, jewelry (beads, cabochons), carvings, and as a popular collector's specimen due to its translucency and color.
Geological facts
Carnelian has been used as a gemstone since the Early Neolithic period; it was highly prized in Ancient Egypt for amulets and in Rome for signet rings because it doesn't stick to hot wax.
Field identification & locations
Identify by its waxy luster, conchoidal fracture (curved breaks), and reddish-brown translucency. Often found in riverbeds or coastal gravels in areas with ancient volcanic activity.
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sedimentary
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
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