sedimentary

Sandstone (Greywacke)

Arenite / Wacke (Mainly SiO2 with various lithic fragments)

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs scale); Color: Dark grey to brownish-grey; Luster: Dull/Earthy; Crystal structure: Granular (clastic texture); Cleavage: None; Specific gravity: 2.6 - 2.7.

Hardness: 6-7 (Mohs scale)
Color: Dark grey to brownish-grey
Luster: Dull/Earthy

Identified March 25, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Dark grey to brownish-grey; Luster: Dull/Earthy; Crystal structure: Granular (clastic texture); Cleavage: None; Specific gravity: 2.6 - 2.7.

Formation & geological history

Formed through the accumulation of sand-sized grains, often in deep-water marine environments (turbidity currents). The presence of poor sorting and matrix suggests a 'dirty' sandstone origin, likely Paleozoic or Mesozoic era.

Uses & applications

Used primarily as crushed stone for road construction, concrete aggregate, and sometimes as a building stone or for landscaping.

Geological facts

Greywacke is often called 'dirty sandstone' because of its high clay and rock fragment content. It often exhibits graded bedding, which tells geologists which way was 'up' when the rock formed millions of years ago.

Field identification & locations

Identify in the field by its gritty texture (feels like sandpaper), visible layering (bedding), and resistance to scratching. Common in mountain belts and coastal regions. Best for collectors when it contains fossils or distinct quartz veining.