sedimentary
Sandstone (Ferruginous)
Arenite (composed primarily of SiO2 with Fe2O3 staining)
Hardness: 6-7 (Mohs scale); Color: Red, orange, tan, or brown; Luster: Dull to earthy; Crystal structure: Clastic (grainy); Cleavage: None; Specific gravity: 2.2–2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Red, orange, tan, or brown
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Red, orange, tan, or brown; Luster: Dull to earthy; Crystal structure: Clastic (grainy); 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. The red/orange hue indicates oxidation of iron minerals (hematite or limonite) within the cementing matrix. Typically found in ancient desert, river, or ocean environments.
Uses & applications
Commonly used as a building material, paving stone, and in glass manufacturing if silica content is high. Also used for decorative landscaping and as an reservoir rock for oil and natural gas.
Geological facts
Sandstone makes up about 20% of all sedimentary rocks on Earth. The spectacular red colors of the Grand Canyon and Zion National Park are due to ferruginous sandstone layers.
Field identification & locations
Identify in the field by its gritty, sandpaper-like texture and visible bedding planes. It often weathers into blocky or rounded outcrops. Found globally in sedimentary basins.
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