sedimentary
Sandstone (Ferruginous)
Arenite (primarily SiO2 with Fe2O3 cement)
Hardness: 6-7 (individual grains); Color: Tan, brown, or reddish due to iron oxides; Luster: Dull/Earthy; Texture: Granular, sandpaper-like feel; Structure: Clastic
- Hardness
- 6-7 (individual grains)
- Color
- Tan, brown, or reddish due to iron oxides
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (individual grains); Color: Tan, brown, or reddish due to iron oxides; Luster: Dull/Earthy; Texture: Granular, sandpaper-like feel; Structure: Clastic
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. The brown coloring suggests secondary enrichment by iron-rich groundwater (limonite or hematite staining) over millions of years, likely in a terrestrial or shallow marine environment.
Uses & applications
Used widely as a building material, paving stone, and in the production of glass (if high silica). In lower grades, it is crushed for road base or used as landscaping stone.
Geological facts
Sandstone can be porous enough to act as an aquifer, holding significant amounts of groundwater or petroleum. The famous Red Rocks of Colorado and the structures of Petra are carved from massive sandstone deposits.
Field identification & locations
Identify in the field by its gritty texture and visible sand grains. It will not fizz with acid unless it has a calcitic cement. Found globally in basins and sedimentary outcroppings.
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