sedimentary
Sandstone (Ferruginous)
Arenite (variable SiO2 with Fe2O3 staining)
Hardness: 6-7 (Mohs scale); Color: Brown, tan, reddish-brown due to iron oxidation; Luster: Dull/Earthy; Crystal structure: Clastic texture; Cleavage: None; Specific gravity: 2.2 - 2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Brown, tan, reddish-brown due to iron oxidation
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Brown, tan, reddish-brown due to iron oxidation; Luster: Dull/Earthy; Crystal structure: Clastic texture; 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. This specific rounded specimen indicates significant transport by water (river or beach) occurring over thousands to millions of years.
Uses & applications
Commonly used as a building material, paving stones, and in glass manufacturing if silica content is high. In this rounded form, it is often used for landscaping or as decorative 'river rock'.
Geological facts
Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The iron oxide (hematite or limonite) acting as a partial cement gives this specimen its distinctive brown color.
Field identification & locations
Identify by its 'sandpaper' feel and visible grains under a hand lens. Commonly found in riverbeds, canyons, and coastal areas. It will not fizz with HCl unless it has a calcite cement.
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