sedimentary

Quartz Veined Siltstone or Graywacke

Clastic Sedimentary Rock with Quartz (SiO2) veining

Hardness: 3-4 (matrix) to 7 (veins); Color: Gray or tan matrix with white quartz veins; Luster: Dull/earthy matrix with vitreous (glassy) veins; Structure: Microcrystalline matrix with irregular hydrothermal crystalline infill.

Hardness: 3-4 (matrix) to 7 (veins)
Color: Gray or tan matrix with white quartz veins
Luster: Dull/earthy matrix with vitreous (glassy) veins

Identified February 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of fine-grained sediment (silt/sand) in a marine or fluvial environment. The white lattice pattern was created later by hydrothermal fluids rich in silica filling cracks (joints) during tectonic activity or burial metamorphism.

Uses & applications

Primarily used in construction as crushed stone or aggregate. High-quality specimens with aesthetic vein patterns are popular as 'yard stones' or decorative garden rocks.

Geological facts

The 'web-like' appearance is a result of differential weathering; the harder quartz veins resist erosion better than the softer surrounding host rock, causing the white lines to protrude from the surface.

Field identification & locations

Identify in the field by the white 'criss-cross' lines that feel harder and more raised than the gray rock around them. Common in mountainous regions or areas with historical tectonic uplift and fluid movement.

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