sedimentary
Sandstone (Ferruginous)
Arenite (with iron oxide cement, Fe2O3)
Hardness: 6-7 (Mohs scale), Color: tan to reddish-brown, Luster: dull/earthy, Crystal structure: granular clastic texture, Cleavage: none, Specific gravity: 2.2-2.8
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Physical properties
Hardness: 6-7 (Mohs scale), Color: tan to reddish-brown, Luster: dull/earthy, Crystal structure: granular 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 specimen shows signs of iron-oxide staining, suggesting formation in an oxidizing environment like a riverbed or desert.
Uses & applications
Commonly used as a construction material (dimension stone), in glass manufacturing if pure silica is present, and as a reservoir rock for oil and gas.
Geological facts
Sandstone accounts for approximately 20% of all sedimentary rocks on Earth. The varied colors are often due to impurities; iron oxides specifically create the red and brown hues.
Field identification & locations
Identify by its 'sandpaper' feel and visible grains. It is common in basin environments worldwide. Collectors often look for unique erosion patterns or fossil inclusions.
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