Red Sandstone (River Cobble)

Hardness 6-7, reddish-brown to terracotta color due to iron oxide (hematite) cement, dull to earthy luster, fine to medium-grained clastic sand texture, smooth disk-like stream-rounded shape.

Formed from the deposition and compaction of quartz sand grains in ancient riverbed, desert dune, or deltaic environments. The red coloration is derived from iron oxide precipitation during diagenesis. Subsequently rounded and smoothed by mechanical stream abrasion over thousands of years.

Commonly used in landscaping, river rock gardens, masonry building stone, aquariums, and decorative outdoor features.

Smooth, flat river rocks like this were historically prized for skipping stones and shaping into primitive tools or grinding stones due to their symmetrical, water-worn shape.

Look for a granular, sandpaper-like texture under magnification with uniform reddish-brown iron staining. Abundant in river valleys, beaches, and glacial gravel deposits globally.