sedimentary
Carnelian Agate
Carnelian (Silicon Dioxide - SiO2)
Hardness: 6.5-7 (Mohs). Color: Translucent orange to reddish-brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.
- Hardness
- 6
- Color
- Translucent orange to reddish-brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs). Color: Translucent orange to reddish-brown. Luster: Waxy to vitreous. Crystal structure: Trigonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.
Formation & geological history
Forms as a secondary mineral in volcanic rocks and sedimentary environments when silica-rich fluids deposit in cavities. The orange color is due to iron oxide impurities (hematite). Many specimens date from the Cenozoic era.
Uses & applications
Used primarily in jewelry as cabochons or beads, ornamental carvings, seals, and as a popular collector specimen for its vibrant color.
Geological facts
Carnelian was used by ancient Egyptians as a protective amulet and by Romans to carve signet rings for wax seals because hot wax does not stick to it.
Field identification & locations
Identify by its waxy luster, translucency, and warm orange-red palette. Common in India, Brazil, Uruguay, and Madagascar. Look for it in river gravels or weathering out of igneous hosts.
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