sedimentary

Sandstone (Ferruginous)

Arenite (primarily SiO2 with iron oxide Fe2O3 cement)

Hardness: 6-7 (Mohs); Color: Tan, brown, and reddish-rust due to iron oxidation; Luster: Dull/Earthy; Crystal Structure: Clastic texture with granular grains; Cleavage: None; Specific Gravity: 2.2-2.8.

Hardness: 6-7 (Mohs)
Color: Tan, brown, and reddish-rust due to iron oxidation
Luster: Dull/Earthy

Identified June 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. The reddish staining indicates the presence of iron oxide (hematite or limonite) acting as a cementing agent, typically in terrestrial or oxidizing environments.

Uses & applications

Commonly used in construction as a building stone or road base. In industry, it can be a source of silica for glassmaking. Crushed sandstone is used in filtration systems.

Geological facts

Sandstone accounts for roughly 20-25% of all sedimentary rocks on Earth. The 'rust' color on this specimen is a natural result of the 'rusting' of iron minerals within the rock when exposed to oxygen and water.

Field identification & locations

Identify in the field by its gritty, sandpaper-like feel and visible grains. Often found in riverbeds, desert dunes, or coastal areas. Collectors look for unique banding patterns (Liesegang rings) or fossils within the layers.

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