metamorphic or sedimentary

Weathered Quartzite or Chert Pebble

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

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

Identified March 15, 2026More metamorphic or sedimentary →

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Physical properties

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.