sedimentary

Weathered sandstone pebble

Ferruginous quartz arenite (iron-stained sandstone)

AI-generated identification · may be incorrect

Composed mainly of quartz grains with clay minerals and iron oxides; typically Mohs 6–7 for quartz but weakly cemented overall. Tan to reddish-brown, dull to earthy luster, porous granular texture, and no obvious cleavage; the rounded shape indicates abrasion or tumbling.

Identified August 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand was compacted and cemented in a sedimentary basin, likely millions to hundreds of millions of years ago; iron-bearing groundwater produced the red staining. Subsequent weathering and stream or beach transport rounded it.

Uses & applications

Common sandstone is used for building stone, paving, aggregate, and landscaping, though this small weathered specimen has mainly educational or decorative value.

Geological facts

The cavity-rich surface reflects differential weathering of softer cement or mineral grains. Red coloration commonly comes from hematite or limonite coatings around quartz grains.

Field identification & locations

Identify it by its gritty texture, visible sand-sized grains, porous weathered surface, and scratch resistance from quartz; it should not fizz strongly in dilute acid. Sandstone pebbles occur widely in riverbeds, beaches, deserts, and glacial deposits.