sedimentary
Sandstone (River Rock)
Arenite (composed primarily of SiO2)
Hardness: 6-7 (on Mohs scale); Color: Tan, buff, and cream with dark grey/black mineral staining or lichen; Luster: Dull/Earthy; Crystal structure: Clastic (granular texture); Cleavage: None; Specific gravity: 2.2-2.8
- Hardness
- 6-7 (on Mohs scale)
- Luster
- Dull/Earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 (on Mohs scale); Color: Tan, buff, and cream with dark grey/black mineral staining or lichen; Luster: Dull/Earthy; Crystal structure: Clastic (granular texture); Cleavage: None; Specific gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments over millions of years. This specific specimen shows signs of fluvial erosion (river rounding) and secondary mineral coating (desert varnish or manganese oxides).
Uses & applications
Used extensively in construction for paving and walling. As a 'river rock,' it is popular in landscaping and decorative masonry.
Geological facts
Sandstone makes up about 20% of all sedimentary rocks on Earth. The dark coloring on the surface is likely Manganese or Iron oxide staining, often referred to as 'desert varnish' when found in arid environments.
Field identification & locations
Identify in the field by its gritty, sandpaper-like texture and visible sand grains. These rounded 'cobbles' are commonly found in ancient or modern riverbeds and glacial outwash plains.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary