sedimentary
Sandstone (Ferruginous)
Arenite with Iron Oxide staining (Fe2O3)
Hardness: 6-7 on Mohs scale; Color: Tan, brown, reddish-orange due to iron oxidation; Luster: Dull, earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 on Mohs scale
- Color
- Tan, brown, reddish-orange due to iron oxidation
- Luster
- Dull, earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Tan, brown, reddish-orange due to iron oxidation; Luster: Dull, earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral particles or rock fragments, typically in riverbeds, deserts, or coastal environments. This specific specimen shows signs of water-rounding, suggesting it was tumbled in a river or beach environment.
Uses & applications
Used widely in construction such as building stones, paving, and flagging. It is also an important reservoir rock for groundwater and petroleum.
Geological facts
Sandstone accounts for roughly 20-25% of all sedimentary rocks on Earth. The red and brown colors are often caused by the presence of iron oxide minerals like hematite or goethite acting as a cement or coating on the grains.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and visible sand grains. These water-worn cobbles are commonly found in glacial till, river deposits, and along coastlines.
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