Ferruginous Sandstone

Physical Properties

Hardness: 6-7 (Mohs); Color: Tan, reddish-brown, or orange due to oxidation; Luster: Dull/Earthy; Crystal Structure: Clastic grainy texture; Cleavage: None (conchoidal to irregular fracture); Specific Gravity: 2.2-2.8.

Formation & Geological History

Formed through the accumulation and compaction of sand-sized mineral grains (usually quartz) where iron-rich waters percolate through, precipitating hematite or goethite as a binding cement. These typically form in fluvial, deltaic, or desert environments.

Uses & Applications

Used primarily in building construction as a durable stone, as a source for low-grade iron ore in historical contexts, and for landscaping or road aggregate.

Geological Facts

The reddish-orange staining is essentially 'rock rust'. Landscapes like the Grand Canyon or the red rocks of Sedona owe their iconic colors to the same iron-oxide minerals found in this specimen.

Field Identification & Locations

Identify in the field by its sandpaper-like feel and the presence of visible grains. It will often leave a reddish or yellowish streak if scratched against a porcelain plate. Found globally in sedimentary basins.

Identified on: 4/13/2026

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