mineral
Chalcedony (Common Opal variant or Agate pebble)
Silicon dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Translucent white to milky cream, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Translucent white to milky cream, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal
Formation & geological history
Formed from the deposition of silica from groundwater in cavities of volcanic rocks or sedimentary formations over millions of years.
Uses & applications
Used in jewelry making as cabochons, for lapidary art, and popular among rock collectors for its smooth texture.
Geological facts
Chalcedony is composed of microscopic crystals of quartz and moganite. When it forms in concentric layers, it is called agate; when it is milky and lacks banding, it is simply common chalcedony.
Field identification & locations
Identify by its waxy luster, conchoidal fracture (smooth curved breaks), and ability to scratch glass. Commonly found in riverbeds, deserts, and volcanic regions worldwide.
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