Sandstone (Graywacke type)

Physical Properties

Hardness: 6-7 on Mohs scale; Color: Gray to greenish-gray; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.6-2.7. It has a gritty, sandpaper-like texture.

Formation & Geological History

Formed from the accumulation of sand-sized mineral grains or rock fragments. This specific type likely formed in deep-water marine environments via turbidity currents where rapid deposition prevents the sorting of minerals.

Uses & Applications

Commonly used as a building stone, road base material, decorative gravel, and occasionally for grindstones or filtering systems due to its abrasive and porous nature.

Geological Facts

Sandstone comprises about 20-25% of all sedimentary rocks on Earth. It is a major reservoir for water (aquifers) and oil/natural gas because of its high porosity.

Field Identification & Locations

Identify it in the field by its 'sandy' feel when rubbed and its visible crystalline grains. It is extremely common worldwide, particularly in mountain belts and river basins.

Identified on: 4/14/2026

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