Sandstone (Ferruginous)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Brownish-red to earthy orange due to iron oxide; Luster: Dull/Earthy; Crystal structure: Clastic (sand grains); Cleavage: None; Specific gravity: 2.2-2.8

Formation & Geological History

Formed through the accumulation and cementation of sand-sized mineral particles (mostly quartz) in ancient riverbeds, deserts, or marine environments. The reddish color indicates the presence of iron oxide (hematite/limonite) during lithification.

Uses & Applications

Used in construction as a building stone, abrasive material, and for landscaping. Ferruginous types are sometimes studied as minor iron ores.

Geological Facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The famous red rock formations in places like Sedona, Arizona, and the Grand Canyon are primarily ferruginous sandstones.

Field Identification & Locations

Identify by its gritty, sandpaper-thick texture. It can be found globally in outcrop formations and riverbeds. Collectors should look for unique cross-bedding patterns or fossil inclusions.

Identified on: 4/13/2026

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