mineral
Chalcedony (Agate / Chert)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Greyish-blue to translucent light blue/grey; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None; Conchoidal fracture
- Hardness
- 6
- Color
- Greyish-blue to translucent light blue/grey
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Greyish-blue to translucent light blue/grey; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None; Conchoidal fracture
Formation & geological history
Formed by the deposition of silica-rich fluids at relatively low temperatures in cavities and fractures of various rock types, including volcanic and sedimentary rocks.
Uses & applications
Used in lapidary arts, jewelry making, tumbling, ornamental carvings, and historical tool making (flint knapping).
Geological facts
Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. Agate is a banded variety of chalcedony.
Field identification & locations
Identified by its waxy luster, smooth conchoidal (shell-like) fracture surfaces, and hardness (scratches glass). Commonly found in gravel beds, volcanic areas, and dry riverbeds worldwide.
