sedimentary
Quartz and Mixed Sedimentary Rocks
Silicon Dioxide (SiO2) mixed with various clastic sedimentary lithologies
Hardness: 7 (for quartz), 3-6 (for others). Color: White, grey, brown, tan. Luster: Vitreous to dull. Structure: Microcrystalline to massive. Cleavage: None (conchoidal fracture common in white pieces).
- Hardness
- 7 (for quartz), 3-6 (for others)
- Color
- White, grey, brown, tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (for quartz), 3-6 (for others). Color: White, grey, brown, tan. Luster: Vitreous to dull. Structure: Microcrystalline to massive. Cleavage: None (conchoidal fracture common in white pieces).
Formation & geological history
Likely sourced from a riverbed, glacial till, or crushed gravel deposit. The white specimens are quartz veins precipitated from hydrothermal fluids, while the grey/brown stones are weathered siltstone or sandstone formed by lithification of sediment.
Uses & applications
Commonly used as construction aggregate, landscaping gravel, or road base material. These are standard specimens found in gardens and driveways.
Geological facts
Quartz is one of the most abundant minerals on Earth's crust and is highly resistant to chemical and physical weathering, which is why it often remains as white pebbles while other minerals erode away.
Field identification & locations
Identify in the field by checking for the white stones' inability to be scratched by a steel blade (quartz) and the layered or grainy texture of the darker sedimentary pieces. Commonly found in backyard play areas and drainage pits.
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Sandstone or Siltstone
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Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
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Shale or Slaty Mudstone
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Sandstone
Arenite (primarily SiO2)
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