mineral
Chalcedony
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale. Color: Pale blue, grey, or white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal). Cleavage: None. Specific Gravity: 2.6-2.64.
- Hardness
- 6
- Color
- Pale blue, grey, or white
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Pale blue, grey, or white. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal). Cleavage: None. Specific Gravity: 2.6-2.64.
Formation & geological history
Formed from the deposition of silica-rich fluids in volcanic cavities, sedimentary rocks, or along hydrothermal veins. It often forms at low temperatures.
Uses & applications
Used primarily in lapidary work for cabochons, beads, and carvings. Also used historically for seals and tools due to its toughness.
Geological facts
Chalcedony is a broad term for cryptocrystalline quartz. Varieties include agate, jasper, and carnelian. It was named after the ancient Greek town of Chalkedon.
Field identification & locations
Identify by its waxy luster, lack of visible crystals, and conchoidal fracture. Often found as nodules or lining geodes. Common in basaltic areas and river beds.
