mineral
Chalcedony (River Stone)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs; Color: Gray, bluish-white; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Gray, bluish-white
- Luster
- Waxy to vitreous
Identified More mineral →
Explore Chalcedony (River Stone) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Gray, bluish-white; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Trigonal/Monoclinic); Cleavage: None; Specific gravity: 2.58-2.64
Formation & geological history
Formed through the precipitation of silica from groundwater in volcanic cavities, sedimentary rocks, or hydrothermal veins. This specific specimen has been rounded and smoothed by water erosion in a river or coastal environment.
Uses & applications
Used in gemstone carving, jewelry making (cabochons), and as a collector's item. Historically used for making tools and seals.
Geological facts
Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen without a microscope. It comes in many varieties including agate, carnelian, and onyx.
Field identification & locations
Identify in the field by its waxy appearance, lack of visible crystals, and extreme hardness (it will scratch glass). Commonly found in dry riverbeds, beaches, and gravel pits.
