mineral
Chalcedony/Agate
Cryptocrystalline Silica (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: honey-brown to tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microscopic); Cleavage: none; Fracture: Conchoidal; Specific Gravity: 2.6
- Hardness
- 6
- Color
- honey-brown to tan
- Luster
- waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: honey-brown to tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microscopic); Cleavage: none; Fracture: Conchoidal; Specific Gravity: 2.6
Formation & geological history
Formed via precipitation of silica-rich fluids in volcanic or sedimentary cavities. This waterworn specimen likely originated from weathered igneous rock and was transported by river or glacial action.
Uses & applications
Used for lapidary work, jewelry, tumbling, and as a collector's specimen. Chalcedony is also used industrially in precision bearings.
Geological facts
Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without high magnification. When semi-translucent and brownish, it is often referred to as carnelian or sard.
Field identification & locations
Check for translucency when held to a light source and a waxy surface texture. Commonly found in riverbeds, gravel pits, and coastal areas throughout the world.
