sedimentary

Sandstone (with Iron Staining)

Clastic sedimentary rock (primarily SiO2)

Hardness: 6-7 (Mohs scale); Color: Cream, tan, or buff with reddish-brown iron oxide patches; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None (breaks across grains); Specific Gravity: 2.2-2.8

Hardness: 6-7 (Mohs scale)
Color: Cream, tan, or buff with reddish-brown iron oxide patches
Luster: Dull/Earthy

Identified April 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of sand-sized silicate grains (quartz and feldspar) in marine, fluvial, or desert environments. This specimen likely dates back millions of years and was cemented by minerals like silica or calcium carbonate.

Uses & applications

Commonly used as a building material, flagstone for paving, and as an abrasive in industrial manufacturing. It is also an important reservoir rock for groundwater and petroleum.

Geological facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The distinct reddish-brown spots seen on this specimen are 'liesegang rings' or simple oxidation (rusting) of iron-bearing minerals within the rock.

Field identification & locations

Identify in the field by its gritty, sandpaper-like feel and visible grains. It provides a record of past surface environments and energy levels of ancient water currents. Found globally in basins and mountainous regions.

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