sedimentary
River Stone (Greywacke)
Greywacke (Lithic Sandstone)
AI-generated identification · may be incorrectHardness: 6-7 (Mohs); Color: Grey, greenish-grey, or brownish; Luster: Dull/Earthy; Structure: Massive, fine to medium-grained; Cleavage: None.
- Hardness
- 6-7 (Mohs)
- Color
- Grey, greenish-grey, or brownish
- Luster
- Dull/Earthy
Identified More sedimentary →
Explore River Stone (Greywacke) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (Mohs); Color: Grey, greenish-grey, or brownish; Luster: Dull/Earthy; Structure: Massive, fine to medium-grained; Cleavage: None.
Formation & geological history
Formed in deep-water marine environments from the rapid deposition of poorly sorted sand, mud, and rock fragments. This specimen has been rounded by fluvial (river) erosion over thousands of years.
Uses & applications
Used primarily in construction aggregate, road base, landscaping, and as decorative river rock in gardens.
Geological facts
Greywacke is often called 'dirty sandstone' because of its high clay and rock fragment content. It often indicates high tectonic activity at the time of its formation.
Field identification & locations
Identify by its salt-and-pepper appearance, dull grey color, and extreme hardness. Commonly found in riverbeds, glacial deposits, and coastal areas.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary