sedimentary

Greywacke with Quartz Veins

Lithic Wacke (SiO2 enriched)

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs); Color: Dark grey matrix with white veins; Luster: Dull/Earthy; Structure: Fine-grained clastic; Cleavage: None; Specific Gravity: 2.6-2.7.

Hardness: 6-7 (Mohs)
Color: Dark grey matrix with white veins
Luster: Dull/Earthy

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs); Color: Dark grey matrix with white veins; Luster: Dull/Earthy; Structure: Fine-grained clastic; Cleavage: None; Specific Gravity: 2.6-2.7.

Formation & geological history

Formed in deep-water marine environments (turbidites) during the Paleozoic to Mesozoic eras. The white veins are later hydrothermal quartz injections into fractures.

Uses & applications

Commonly used as crushed stone for road base, concrete aggregate, and coastal protection (rip-rap). Small water-worn pebbles are used decoratively in landscaping.

Geological facts

Greywacke is often called 'dirty sandstone' because it contains a mix of poorly sorted grains and clay. The distinctive white 'wishing lines' are quartz filled into tectonic cracks.

Field identification & locations

Identify by its 'salt and pepper' appearance and hardness (it will scratch glass). Commonly found in mountainous fold belts and along rocky coastlines like the UK or New Zealand.