Sandstone (Ferruginous)

Physical Properties

Hardness: 6-7 (Mohs); Color: Tan, yellow, or rusty brown due to iron oxidation; Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None, breaks across grains.

Formation & Geological History

Formed from the accumulation and lithification of sand-sized grains (mostly quartz) in environments like deserts, riverbeds, or beaches. The yellowish-brown color indicates exposure to oxygen and water, causing iron minerals to oxidize.

Uses & Applications

Commonly used in construction as a building material, paving stones, and for making glass (if silica content is high). Large-grained varieties are used for grindstones.

Geological Facts

Sandstone is one of the most common sedimentary rocks on Earth. It often contains fossils and serves as a significant reservoir for groundwater, oil, and natural gas due to its porosity.

Field Identification & Locations

Identify in the field by its gritty, sandpaper-like feel. It can be found in mountain ranges, canyons, and desert regions globally. Collectors often look for examples with unique weathering patterns or 'Liesegang rings'.

Identified on: 4/15/2026

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