sedimentary
Sandstone (Iron-stained)
Arenite (composed primarily of SiO2 with Fe2O3 staining)
Hardness: 6-7 (Mohs scale); Color: Tan to grey with orange/brown rust-colored oxidation; Luster: Dull or earthy; Crystal structure: Granular/clastic; Cleavage: None; Specific Gravity: 2.2–2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Tan to grey with orange/brown rust-colored oxidation
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Tan to grey with orange/brown rust-colored oxidation; Luster: Dull or earthy; Crystal structure: Granular/clastic; Cleavage: None; Specific Gravity: 2.2–2.8
Formation & geological history
Formed through the accumulation and cementation of mineral particles or rock fragments (clasts) the size of sand. The orange coloration is due to the oxidation of iron-bearing minerals (limonite or hematite) within the rock. Typical ages range from millions to hundreds of millions of years old.
Uses & applications
Used widely in the construction industry for building materials and road base. Fine-grained varieties are used for making glass and in metal casting. Primarily a landscape or garden rock when found in this weathered cobble form.
Geological facts
Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The 'rust' on this specimen indicates it has been exposed to water and oxygen for a significant period, causing the iron minerals to oxidize.
Field identification & locations
Identify in the field by its gritty, sandpaper-like texture and visible grains. Often found in riverbeds or coastal areas as rounded 'river rocks' due to water erosion. Significant for collectors as indicators of ancient environments like deserts or beaches.
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