sedimentary

Arkosic Sandstone

Arkose (Clastic Sedimentary Rock)

Hardness: 6-7 on Mohs scale (due to quartz/feldspar content); Color: Pink to reddish-brown (from potassium feldspar and iron oxides); Luster: Dull/Earthy; Structure: Coarse-grained, clastic; Specific Gravity: 2.5–2.7.

Hardness: 6-7 on Mohs scale (due to quartz/feldspar content)
Luster: Dull/Earthy

Identified February 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the rapid erosion and short-distance transport of granitic rocks, preventing the weathering of feldspar. Typically found in alluvial fans or rift basins. Common in Paleozoic and Mesozoic geological formations.

Uses & applications

Used primarily as construction aggregate, road base, and occasionally as building stone. While not used in jewelry, it is a key indicator for petroleum and uranium deposits in geological exploration.

Geological facts

Arkosic sandstone is often referred to as 'dirty granite' because it contains more than 25% feldspar, which is unusual for sandstone. Famous formations include the Flatirons in Colorado and Uluru (Ayers Rock) in Australia.

Field identification & locations

Identify in the field by its gritty texture and the presence of visible pinkish-orthoclase feldspar grains. Commonly found near mountainous regions or ancient fault lines. Fragments are angular, indicating it hasn't traveled far from its source rock.

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