sedimentary

Sandstone (Greywacke)

Clastic Sedimentary Rock (SiO2 with lithic fragments)

AI-generated identification · may be incorrect

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

Identified April 1, 2026More sedimentary →

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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.