sedimentary

Quartz-Veined Mudstone

Argillite or Mudstone with Quartz Veining (SiO2 in Siliciclastic Matrix)

AI-generated identification · may be incorrect

Hardness: 3-4 (matrix) / 7 (veins); Color: Reddish-brown matrix with white/cream veins; Luster: Dull to earthy; Structure: Fine-grained clastic; Cleavage: None (conchoidal fracture on veins)

Hardness: 3-4 (matrix) / 7 (veins)
Color: Reddish-brown matrix with white/cream veins
Luster: Dull to earthy

Identified June 3, 2026More sedimentary →

Explore Quartz-Veined Mudstone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3-4 (matrix) / 7 (veins); Color: Reddish-brown matrix with white/cream veins; Luster: Dull to earthy; Structure: Fine-grained clastic; Cleavage: None (conchoidal fracture on veins)

Formation & geological history

Formed from the lithification of silt and clay. The characteristic white lines (veins) were created when tectonic stress caused the rock to fracture, allowing silica-rich hydrothermal fluids to circulate through the cracks and crystallize into quartz.

Uses & applications

Commonly used as decorative garden stones, in landscaping, or as tumbling rough for amateur geologists. Occasionally used as low-grade construction fill.

Geological facts

The 'spiderweb' pattern of veins is a record of ancient seismic or tectonic activity. These specimens are often water-worn, smoothed by the action of rivers or beaches.

Field identification & locations

Identify in the field by looking for fine-grained dark rocks intersected by hard, light-colored mineral lines that cannot be scratched by a steel knife. Frequently found in riverbeds and coastal regions.