sedimentary
Carnelian Agate
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs scale; Color: Red-orange to brownish-red; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Red-orange to brownish-red
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 Mohs scale; Color: Red-orange to brownish-red; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.64
Formation & geological history
Formed as a result of groundwater carrying silica-rich fluids through cavities in volcanic or sedimentary rocks, often in hydro-thermal environments. Its color comes from iron oxide impurities.
Uses & applications
Used primarily in lapidary art for cabochons, beads, and jewelry. Also used historically for signet rings and wax seals because hot wax does not stick to it.
Geological facts
Carnelian was one of the first stones used by humans for jewelry, dating back to the Neolithic period. Ancient Egyptians believed it helped souls pass into the afterlife.
Field identification & locations
Identify in the field by its waxy luster, translucency, and warm reddish-orange hues. Common in riverbeds and coastal regions such as the American Northwest or Brazil.
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