mineral
Chalcedony (Tumbled)
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs scale); Color: Translucent grey to tan/apricot; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (microscopic); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Translucent grey to tan/apricot
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Translucent grey to tan/apricot; Luster: Waxy to vitreous; Crystal structure: Trigonal/Monoclinic (microscopic); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64
Formation & geological history
Formed via the low-temperature deposition of silica-rich groundwater in cavities of other rocks, particularly volcanic and sedimentary environments. Can be millions of years old, often found in Cenozoic deposits.
Uses & applications
Used extensively in jewelry as beads and cabochons, for ornamental carvings, and historically for making tools or seals due to its toughness.
Geological facts
Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without a microscope. Agate and Jasper are both varieties of chalcedony.
Field identification & locations
Identify in the field by its waxy luster, smoothness, and 'conchoidal' (shell-like) fracture patterns. It is frequently found as nodules in river beds or volcanic fields in locations like Brazil, India, and the United States.
