sedimentary

Sandstone with Iron Oxide Coating

Arenite (SiO2 with Fe2O3 impurities)

Mohs hardness: 6-7 (quartz grains) with softer matrix; Color: reddish-brown, tan, and cream; Luster: dull to earthy; Texture: clastic (gritty like sandpaper); Structure: masssive to layered crystalline grains.

Hardness: 6-7 (quartz grains) with softer matrix
Color: reddish-brown, tan, and cream
Luster: dull to earthy

Identified July 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation and lithification of sand-sized mineral grains or rock fragments. The reddish hue is due to later-stage iron oxide staining or hematite cementation during diagenesis in oxygen-rich environments.

Uses & applications

Used extensively in construction (as building stone), as a source of silica for glass manufacturing, and as an abrasive. Small specimens are used as teaching aids for sedimentary geology.

Geological facts

Sandstone can be highly porous and often acts as a significant aquifer for groundwater or a reservoir for oil and natural gas. It accounts for about 10-25 percent of all sedimentary rocks on Earth.

Field identification & locations

Identify in the field by its gritty texture (feels like sandpaper when rubbed) and visible sand grains. Found globally in deserts, riverbeds, and coastal regions. Avoid soaking in acid as some cements may dissolve.

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