sedimentary
Ferruginous Sandstone (Grit)
Clastic Sedimentary (Ironstone-rich Sandstone)
Hardness: 6-7 (Mohs scale), Color: Rusty orange/brown, Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Specific Gravity: approx 2.5-3.0.
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Rusty orange/brown, Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Specific Gravity: approx 2.5-3.0.
Formation & geological history
Formed through the accumulation of sand-sized grains (mostly quartz) cemented by iron oxides like limonite or hematite. Usually occurs in riverbed or shallow marine environments where iron-rich water precipitates minerals between grains.
Uses & applications
Used primarily as low-grade construction aggregate, fill dirt, or crushed stone for road base. In some areas, high iron concentrations are mined as iron ore.
Geological facts
The reddish-orange tint is due to the oxidation of iron, essentially geological 'rusting'. These small fragments are often called 'ironstone' by collectors or 'grit' in common terminology.
Field identification & locations
Identify by its gritty texture and characteristic orange-brown rub-off. Found commonly in sedimentary basins, creek beds, and construction sites. Look for the 'streak test' (reddish or brown) on a porcelain plate.
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