mineral
Chalcedony (Common Agate)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on the Mohs scale; Color: Translucent white to light gray; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (hexagonal system); Cleavage: None; Fracture: Conchoidal.
- Hardness
- 6
- Color
- Translucent white to light gray
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale; Color: Translucent white to light gray; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (hexagonal system); Cleavage: None; Fracture: Conchoidal.
Formation & geological history
Forms from the deposition of silica-rich groundwater in cavities of igneous rocks or through sedimentary replacement of organic materials. Found in volcanic environments and river beds worldwide.
Uses & applications
Used primarily in lapidary work for cabochons, beads, and carvings. Also historically used for making seals, mortars and pestles, and as a semi-precious gemstone in jewelry.
Geological facts
Chalcedony is the cryptocrystalline form of quartz, meaning its crystals are too small to be seen with a standard microscope. It has been used by humans for toolmaking and ornamentation since the Bronze Age.
Field identification & locations
Identify by its waxy luster, translucency, and inability to be scratched by a steel knife. Common in volcanic regions and river gravels. Collectors should look for smoothness and light passing through the edge.
