sedimentary
Sandstone (Ferruginous)
Arenite with Iron Oxide cement (SiO2 + Fe2O3)
Hardness: 6-7 (Mohs); Color: Tan, yellow, or rusty brown due to iron oxidation; Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None, breaks across grains.
- Hardness
- 6-7 (Mohs)
- Color
- Tan, yellow, or rusty brown due to iron oxidation
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Tan, yellow, or rusty brown due to iron oxidation; Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None, breaks across grains.
Formation & geological history
Formed from the accumulation and lithification of sand-sized grains (mostly quartz) in environments like deserts, riverbeds, or beaches. The yellowish-brown color indicates exposure to oxygen and water, causing iron minerals to oxidize.
Uses & applications
Commonly used in construction as a building material, paving stones, and for making glass (if silica content is high). Large-grained varieties are used for grindstones.
Geological facts
Sandstone is one of the most common sedimentary rocks on Earth. It often contains fossils and serves as a significant reservoir for groundwater, oil, and natural gas due to its porosity.
Field identification & locations
Identify in the field by its gritty, sandpaper-like feel. It can be found in mountain ranges, canyons, and desert regions globally. Collectors often look for examples with unique weathering patterns or 'Liesegang rings'.
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