mineral
Chalcedony (Agate Pebble)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Translucent pale yellow to grayish; Luster: Waxy to vitreous; Structure: Cryptocrystalline (hexagonal crystal system at microscopic level); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Translucent pale yellow to grayish
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Translucent pale yellow to grayish; Luster: Waxy to vitreous; Structure: Cryptocrystalline (hexagonal crystal system at microscopic level); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64
Formation & geological history
Formed from the deposition of silica-rich groundwater in cavities of volcanic or sedimentary rocks. This specific specimen appears to be a water-worn river pebble, having been smoothed by fluvial transport.
Uses & applications
Used primarily in lapidary work for making beads, cabochons, and decorative carvings. Industrial uses include mortars and pestles for chemical labs due to its hardness.
Geological facts
Chalcedony has been used since the Bronze Age for seal stones and jewelry because it does not stick to wax. It is the broad term for all microcrystalline quartz varieties including agate, carnelian, and onyx.
Field identification & locations
Commonly found in river beds or areas with volcanic history. Can be identified by its waxy luster, translucency when held to light, and its inability to be scratched by a steel knife.
