mineral
Quartz pebble (Agate / Chalcedony)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Grayish-tan to translucent brownish; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Grayish-tan to translucent brownish
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-tan to translucent brownish; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the deposition of silica from water in cavities within igneous or sedimentary rocks, then weathered and water-worn into a smooth river pebble.
Uses & applications
Commonly used in lapidary work, decorative rock collections, tumbling, and landscape ornamentation.
Geological facts
Cryptocrystalline quartz varieties like agate and chalcedony are composed of submicroscopic crystals, making them tough and highly resistant to physical weathering.
Field identification & locations
Identified by its translucency, hardness (scratches glass easily), waxy luster, and smooth, water-rounded shape. Very common in riverbeds, beach gravels, and glacial deposits worldwide.
