sedimentary

Red Sandstone

Quartz Arenite / Arkose Sandstone (SiO2 rich)

Hardness: 6 to 7 (quartz grains); Color: Red, reddish-brown, pinkish due to iron oxide (hematite) cement; Luster: Dull to earthy; Crystal structure: Clastic (composed of cemented mineral particles or rock fragments rather than interlocking crystals); Specific gravity: 2.2 to 2.8

Hardness: 6 to 7 (quartz grains)
Luster: Dull to earthy

Identified July 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation, compaction, and cementation (lithification) of sand-sized mineral particles, most commonly quartz, often in desert dune or ancient river/shallow marine environments over millions of years.

Uses & applications

Widely used in construction, architectural building stone, paving, retaining walls, and previously for grindstones.

Geological facts

The characteristic red color is caused by iron oxide coatings on the sand grains, often indicating deposition in a terrestrial, oxygen-rich environment such as a desert.

Field identification & locations

Easily identified by its gritty, sandpaper-like texture and visible sand grains. Found worldwide in sedimentary basins and geological formations like the American Southwest.

Other sedimentary specimens

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Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

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Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Banded Siltstone / Mudstone Pebble

Siltstone / Argillite

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Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)

sedimentary

Shale

Shale (clastic sedimentary rock)

sedimentary