sedimentary
Sandstone
Arenite (SiO2 composed primarily of quartz)
Mohs hardness 6-7, reddish-brown color due to iron oxide inclusions, dull to earthy luster, visible sand-sized grains, grainy textured fracture
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Physical properties
Mohs hardness 6-7, reddish-brown color due to iron oxide inclusions, dull to earthy luster, visible sand-sized grains, grainy textured fracture
Formation & geological history
Formed by the accumulation and compaction of sand-sized grains of mineral, rock, or organic material in environments such as deserts, beaches, and river beds over millions of years.
Uses & applications
Extensively used as a building and paving material, in decorative masonry, as an aquifer for water, and in glass manufacturing or oil reservoirs.
Geological facts
Red sandstone gets its signature reddish hue from small amounts of iron oxide (rust) coating the quartz sand grains. Entire geological formations like the Grand Canyon display massive layers of sandstone.
Field identification & locations
Identified by its gritty sandpaper-like feel and visible quartz grains. Found abundantly worldwide in exposed bedrock, cliffs, and quarries. Collectors look for unique banding and fossil inclusions.
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