metamorphic or sedimentary
Weathered Quartzite or Chert Pebble
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: White, grey, with tan staining; Luster: Dull to vitreous; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: Roughly 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- White, grey, with tan staining
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: White, grey, with tan staining; Luster: Dull to vitreous; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: Roughly 2.65.
Formation & geological history
Formed from the metamorphism of quartz sandstone (quartzite) or precipitation of silica-rich fluids (chert). This specimen shows rounding and surface frosting consistent with fluvial (stream) or glacial transport over thousands to millions of years.
Uses & applications
Used primarily in construction as aggregate or road base. In smaller forms, these are part of garden landscaping and aquarium substrate. Historically, chert was used for flint-knapping tools.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Specimens like this are often 'survivor' rocks—because they are so hard and chemically stable, they remain intact long after softer surrounding rocks have eroded away.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its lack of reaction to acid. It is commonly found in riverbeds, gravel pits, and coastal beaches globally. Collectors often look for these as 'base' rocks for tumbling.
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Quartz
Quartz (SiO2 - Silicon Dioxide)
Mineral
Milky Quartz
Quartz (Silicon Dioxide, SiO2)
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Milky Quartz
Quartz (Silicon Dioxide - SiO2)
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Milky Quartz
Silicon Dioxide (SiO2)
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Silicon Dioxide (SiO2)
mineral
Pebble (likely Quartz or Chert)
SiO₂ (Silicon Dioxide) - referring to the likely main mineral composition, Quartz. If it's chert, the scientific name remains SiO₂ with a microcrystalline structure.
Sedimentary Rock