Sandstone (with manganese staining)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Tan, beige with black/dark grey dendritic staining; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8

Formation & Geological History

Formed through the accumulation, compaction, and cementation of sand-sized mineral grains or rock fragments. The dark staining is likely manganese oxide, which precipitates from groundwater flowing through the rock's pores.

Uses & Applications

Common sandstone is used in construction as building stone, pavers, or crushed for road base. Specimens with unique patterns are kept by hobbyist collectors.

Geological Facts

Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The dark 'smudges' or tree-like patterns often seen on them are frequently mistaken for plant fossils, but are actually mineral growths called dendrites.

Field Identification & Locations

Identify by its gritty, sandpaper-like feel and visible grains. Often found in riverbeds, deserts, and coastal areas. It will not react with acid unless the cementing material is calcite.

Identified on: 4/21/2026

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