sedimentary

Rounded brown cobble, likely weathered sandstone or iron-rich sedimentary rock

Indeterminate; possibly ferruginous sandstone or ironstone

AI-generated identification · may be incorrect

Brown, dull to earthy luster, rounded by abrasion, and apparently fine-grained; hardness likely about 4–7 Mohs depending on composition. No visible crystals or cleavage are apparent, and the image is insufficient for reliable mineral identification.

Identified August 17, 2026More sedimentary →

Explore Rounded brown cobble, likely weathered sandstone or iron-rich sedimentary rock in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Likely formed by sediment cementation and later rounded through stream, beach, or glacial transport; age and exact environment cannot be determined visually. Iron-oxide staining probably produces the reddish-brown color.

Uses & applications

Common pieces have little commercial value, though sandstone and ironstone are used as aggregate, building stone, paving, and decorative material. This specimen has no evident gemstone or ornamental-grade features.

Geological facts

The smooth shape indicates prolonged mechanical weathering, while mottled coloration may reflect variable iron-oxide cement or weathering. A fresh broken surface would reveal grain size and cement more clearly.

Field identification & locations

Inspect texture with a hand lens, test streak on unglazed porcelain, and check reaction to dilute hydrochloric acid; a steel nail tests approximate hardness. Commonly found in streambeds, beaches, and gravel deposits.