sedimentary
Sandstone (Graywacke)
Clastic Sedimentary Rock (Lithic Sandstone)
Hardness: 6-7 (Mohs); Color: Gray to tan; Luster: Dull/Earthy; Crystal structure: Clastic (composed of mineral grains or rock fragments); Cleavage: None; Specific gravity: 2.2 - 2.8
- Hardness
- 6-7 (Mohs)
- Color
- Gray to tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Gray to tan; Luster: Dull/Earthy; Crystal structure: Clastic (composed of mineral grains or rock fragments); Cleavage: None; Specific gravity: 2.2 - 2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains and rock fragments in marine or fluvial environments. Usually formed under rapid deposition conditions.
Uses & applications
Used in construction as a building stone, road aggregate, and for making concrete. Some varieties are used in landscaping or as decorative garden stones.
Geological facts
Graywacke is often referred to as 'dirty sandstone' because it contains a mix of many different types of rock fragments and minerals rather than just pure quartz.
Field identification & locations
Identify by its gritty texture (feels like sandpaper) and visible grains. Often found in riverbeds or coastal cliffs. Common in areas with tectonic activity where sediment is buried quickly.
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