sedimentary
Sandstone (with Iron Staining)
Clastic sedimentary rock (High Silica / Iron Oxide)
Hardness: 6-7 (Mohs scale); Color: Brownish-tan to reddish-brown; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: approx. 2.2-2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Brownish-tan to reddish-brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Brownish-tan to reddish-brown; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: approx. 2.2-2.8
Formation & geological history
Formed from the accumulation and cementation of sand-sized mineral grains, primarily quartz and feldspar, often in deserts, riverbeds, or coastal environments. The color suggests iron-rich groundwater precipitation (limonite or hematite) during or after lithification.
Uses & applications
Commonly used as a building material, paving stone, and abrasive. Because it is porous, it often acts as an aquifer for water or a reservoir for oil and gas.
Geological facts
Sandstone makes up about 20% of all sedimentary rocks on Earth. The famous 'Red Rocks' in Colorado and the Treasury at Petra are carved out of or composed of sandstone layers.
Field identification & locations
Identify by its gritty, 'sandpaper' feel and visible grains. Often shows layering or cross-bedding. Common in areas with exposed sedimentary basins or near ancient coastlines.
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