sedimentary
Banded River Rock with Quartz Vein
Siltstone/Greywacke with Quartz (SiO2)
Hardness: 6-7 (quartz vein area) vs 4-5 (matrix); Color: Dark grey matrix with white banding; Luster: Dull/Earthy matrix, Vitreous vein; Texture: Fine-grained with crystalline stripes
- Hardness
- 6-7 (quartz vein area) vs 4-5 (matrix)
- Color
- Dark grey matrix with white banding
- Luster
- Dull/Earthy matrix, Vitreous vein
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Physical properties
Hardness: 6-7 (quartz vein area) vs 4-5 (matrix); Color: Dark grey matrix with white banding; Luster: Dull/Earthy matrix, Vitreous vein; Texture: Fine-grained with crystalline stripes
Formation & geological history
Formed through the lithification of fine sediments where later hydrothermal activity forced silica-rich fluids into cracks, cooling to create white quartz veins.
Uses & applications
Primarily used for decorative landscaping, gravel, or as an educational piece to demonstrate geologic cross-cutting relationships.
Geological facts
The white stripe is a 'vein' which is actually younger than the dark rock surrounding it; it represents a 'fossilized' crack filled with mineral-rich water.
Field identification & locations
Commonly found in riverbeds or glacial deposits; identified by the distinct contrast between the dark host rock and the protruding or flush white mineral bands.
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