sedimentary
Sandstone (Ferruginous)
Clastic sedimentary rock (primarily SiO2 with Fe2O3 cement)
Hardness: 6-7 (Mohs scale), Color: Brownish-red to tan (due to iron oxide), Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Cleavage: None, Specific Gravity: 2.0-2.6
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Brownish-red to tan (due to iron oxide), Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Cleavage: None, Specific Gravity: 2.0-2.6
Formation & geological history
Formed from the accumulation and cementation of sand-sized mineral grains or rock fragments. The reddish-brown tint suggests oxidation (rusting) of iron minerals within the pore spaces over geological time, typically in terrestrial or shallow marine environments.
Uses & applications
Common sandstone is used in construction as building stone, pavers, and as a source of silica for glass manufacturing. Smaller specimens are primarily used for educational or basic collection purposes.
Geological facts
Sandstone makes up about 20% of all sedimentary rocks on Earth. The famous red rocks of the Grand Canyon and Zion National Park are composed largely of this type of iron-stained sandstone.
Field identification & locations
Identify in the field by its gritty, sandpaper-like feel. It can often be scratched by a steel blade, but the individual quartz grains themselves are very hard. Look for visible layers (bedding) or cross-bedding in larger outcrops.
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