sedimentary
Sandstone (Greywacke)
Clastic Sedimentary Rock (SiO2 with lithic fragments)
Hardness: 6-7 Mohs; Color: Dull grey to olive-brown; Luster: Earthy to dull; Crystal structure: Clastic (granular); Cleavage: None; Specific gravity: 2.6-2.7.
- Hardness
- 6-7 Mohs
- Color
- Dull grey to olive-brown
- Luster
- Earthy to dull
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Physical properties
Hardness: 6-7 Mohs; Color: Dull grey to olive-brown; Luster: Earthy to dull; Crystal structure: Clastic (granular); Cleavage: None; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the lithification of sand-sized grains, often in marine environments where rapid deposition occurs (turbidity currents). These water-worn pebbles are usually from the Paleozoic or Mesozoic eras.
Uses & applications
Used primarily in construction as aggregate, road base, and occasionally as decorative garden stones. If particularly hard, it can be used for sharpening tools.
Geological facts
This specimen is a 'river rock' or 'beach pebble,' meaning its rounded shape is the result of mechanical weathering and abrasion by water over many years.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and its ability to scratch glass if rich in quartz. It is extremely common in riverbeds and along coastlines globally.
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