sedimentary

Ferruginous Sandstone (with Iron Oxide staining)

Clastic Sedimentary Rock - Quartz Arenite/Wacke

AI-generated identification · may be incorrect

Hardness: 6-7 (Mohs scale for individual quartz grains); Color: Reddish-brown, rusty orange, and dark grey; Luster: Dull/Earthy; Crystal structure: Granular/Clastic texture; Cleavage: None (fractures around grains).

Hardness: 6-7 (Mohs scale for individual quartz grains)
Color: Reddish-brown, rusty orange, and dark grey
Luster: Dull/Earthy

Identified March 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation, compaction, and cementation of sand-sized mineral grains or rock fragments. The reddish-brown coloration is due to the presence of iron oxide (hematite or limonite) acting as a cementing agent or staining the grains. These often date from the Paleozoic to Mesozoic eras depending on the local basin.

Uses & applications

Used primarily as construction aggregate, low-grade building stone, or decorative landscaping rock. Some variants with high iron content were historically used as iron ore (bog iron).

Geological facts

Iron-rich sandstones are what give the American Southwest its famous red rock landscapes, such as those in Sedona or the Grand Canyon. The color is essentially 'rust' on a geological scale.

Field identification & locations

Identify in the field by its sandpaper-like gritty feel and the way it may leave a reddish streak if rubbed against a harder white surface. Common in riverbeds, glacial till, and sedimentary basins. It is often found as 'float' (loose rock) in areas with eroded sandstone bedrock.