sedimentary

Banded River Rock with Quartz Vein

Siltstone/Greywacke with Quartz (SiO2)

AI-generated identification · may be incorrect

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

Identified June 13, 2026More sedimentary →

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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.