mineral
Carnelian / Agate
Silicon Dioxide (SiO2) - Chalcedony variety
Hardness: 6.5-7 on Mohs scale; Color: reddish-orange, brownish-red, amber; Luster: waxy to vitreous; Crystal Structure: Trigonal (microcrystalline quartz); Cleavage: none, displays conchoidal fracture
- Hardness
- 6
- Color
- reddish-orange, brownish-red, amber
- Luster
- waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: reddish-orange, brownish-red, amber; Luster: waxy to vitreous; Crystal Structure: Trigonal (microcrystalline quartz); Cleavage: none, displays conchoidal fracture
Formation & geological history
Formed in volcanic host rocks through the deposition of silica-rich fluids at low temperatures inside cavities, gas vesicles, and fractures.
Uses & applications
Widely used in lapidary work, jewelry making, beads, cabochons, and decorative carvings.
Geological facts
Carnelian has been used as a gemstone for over 4,500 years, notably in ancient Egyptian amulets, Roman signet rings, and Sumerian jewelry.
Field identification & locations
Look for a smooth, waxy feel, translucent to semi-translucent reddish-brown tone, and a curved, shell-like (conchoidal) fracture pattern. Commonly found in riverbeds, gravel deposits, and weathered volcanic basalt formations worldwide.
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Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
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Potassium Feldspar (Orthoclase)
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Mineral