mineral
Chalcedony (Agate)
Chalcedony (Cryptocrystalline Quartz, SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Yellow-orange to brownish-red, Luster: Waxy to vitreous, Crystal Structure: Hexagonal (trigonal), Cleavage: None, Fracture: Conchoidal.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Yellow-orange to brownish-red, Luster: Waxy to vitreous, Crystal Structure: Hexagonal (trigonal), Cleavage: None, Fracture: Conchoidal.
Formation & geological history
Formed via the deposition of silica-rich water in cavities and cracks of volcanic rocks or sedimentary environments. It is often found as nodules or water-worn pebbles.
Uses & applications
Commonly used for lapidary work, jewelry (cabochons), and collection specimens. Historically used for making tools and seals.
Geological facts
The name 'Chalcedony' comes from the Latin 'chalcedonius', derived from the name of the ancient Greek town Chalcedon. Agate is a variety of chalcedony characterized by banding or translucence.
Field identification & locations
Identify by its waxy luster, hardness (will scratch glass), and lack of visible crystals. Commonly found in riverbeds, gravel pits, and desert regions.
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