mineral
Quartz Pebble (possibly Chalcedony or Chert)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-blue, lavender, or tan; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-blue, lavender, or tan
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-blue, lavender, or tan; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed by the precipitation of silica from groundwater in cavities of other rocks or through the accumulation of silica-rich marine organisms. This smooth shape is the result of water erosion in a river or beach environment.
Uses & applications
Commonly used as decorative garden stones, in lapidary art (tumbled stones), and historically as a tool-making material due to its hardness.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Specimens like this that are microcrystalline (crystals too small to see) are often called chalcedony.
Field identification & locations
Identifiable by its smoothness, lack of visible crystals, and ability to scratch glass. Commonly found in riverbeds, gravel pits, and along shorelines worldwide.
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