sedimentary
Sandstone with Iron Staining
Arenite (SiO2 with Fe-oxide coatings)
Hardness: 6.5-7 (Mohs); Color: Tan, brownish-gold, and reddish-brown; Luster: Dull/Earthy; Structure: Clastic; Texture: Gritty/Grainy; Specific Gravity: 2.2-2.8
- Hardness
- 6
- Color
- Tan, brownish-gold, and reddish-brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Tan, brownish-gold, and reddish-brown; Luster: Dull/Earthy; Structure: Clastic; Texture: Gritty/Grainy; Specific Gravity: 2.2-2.8
Formation & geological history
Formed from the accumulation of sand-sized mineral particles or rock fragments, cemented together by silica or minerals like limonite and hematite. The reddish-brown patches are evidence of iron oxidation (chemical weathering).
Uses & applications
Primarily used as a building material, road base, or for architectural stone; also serves as a critical reservoir for water or petroleum in geological formations.
Geological facts
Sandstone represents about 20-25% of all sedimentary rocks on Earth. The 'rusty' brown patches on this specimen are often called 'desert varnish' or iron staining, occurring when iron-rich minerals react with oxygen.
Field identification & locations
Identify in the field by its sandpaper-like feel and visible grains. It is often found in desert environments, riverbeds, and sedimentary basins worldwide. This specific specimen shows weathering rinds.
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