sedimentary
Quartz Pebble (Chert/Chalcedony variety)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Creamy white to pale yellow; Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Creamy white to pale yellow
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Creamy white to pale yellow; Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the precipitation of silica in sedimentary environments or as nodules in limestone/chalk. This specimen appears water-worn and smoothed, likely from a riverbed or coastal environment.
Uses & applications
Common varieties are used in landscaping, as abrasives, and in the manufacturing of glass and ceramics. Polished stones are used in folk jewelry and as 'pocket stones'.
Geological facts
Quartz is one of the most abundant minerals in Earth's crust. Microcrystalline varieties like this have been used since the Stone Age to create tools because of their hardness and predictable fracture patterns.
Field identification & locations
Identify by its ability to scratch glass and its smooth, waxy texture. Commonly found in gravel pits, beaches, and creek beds globally. For collectors, it is a basic foundational specimen.
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