sedimentary

Sandstone Cobble with Iron Staining

Arenite with Limonite/Hematite staining

AI-generated identification · may be incorrect

Hardness: 6-7 (on Mohs scale for quartz grains); Color: Orange-brown, reddish-tan; Luster: Dull, earthy; Crystal structure: Granular/clastic; Specific Gravity: 2.2-2.8

Hardness: 6-7 (on Mohs scale for quartz grains)
Color: Orange-brown, reddish-tan
Luster: Dull, earthy

Identified July 21, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (on Mohs scale for quartz grains); Color: Orange-brown, reddish-tan; Luster: Dull, earthy; Crystal structure: Granular/clastic; Specific Gravity: 2.2-2.8

Formation & geological history

Formed from compressed sand grains cemented by silica or calcite, later weathered by water action causing a rounded shape (cobble). The orange color is due to iron oxide staining from exposure to oxygen and moisture.

Uses & applications

Primarily used in landscaping, road base, and construction. Small cobbles have little industrial value but are used for decorative gardens.

Geological facts

The orange hue is essentially 'rock rust,' where iron-bearing minerals within or on the rock have oxidized. Sandstone makes up about 20% of all sedimentary rocks on Earth.

Field identification & locations

Identify by its gritty, sandpaper-like texture and visible sand grains. These are commonly found in riverbeds, glacial till, and coastal areas. Collectors look for unique banding or patterns caused by the iron staining.