sedimentary

Red sandstone pebble

Ferruginous quartz arenite (iron-oxide-cemented sandstone)

AI-generated identification · may be incorrect

Typically Mohs hardness 6–7 for quartz grains, with a dull to earthy luster; reddish-brown color comes from hematite or goethite coating/cement. Usually clastic and granular, with little or no cleavage; the specimen appears rounded and naturally weathered.

Identified September 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when sand-sized quartz grains were deposited, compacted, and cemented, with iron oxides producing the red coloration. Its exact geological age cannot be determined from the image; red sandstones occur from Precambrian to Recent deposits in deserts, river systems, and coastal basins.

Uses & applications

Used as building stone, paving, aggregate, and decorative rock; attractive pieces may be collected as landscape or educational specimens. It has little gemstone value unless unusually patterned or polished.

Geological facts

The red color is commonly called “rust” in geological terms and reflects oxidizing conditions during or after deposition. Cracks may result from weathering, drying, or minor stress in the original rock.

Field identification & locations

Identify it by its reddish color, gritty texture, rounded pebble form, and possible quartz grains; it should not fizz with dilute hydrochloric acid unless carbonate cement is present. Common in desert gravels, streambeds, and sandstone outcrops worldwide.