Ferruginous Sandstone Pebble

Hardness: 6-7 (Mohs scale), Color: Brownish-red to tan, Luster: Dull/Earthy, Texture: Clastic (fine-grained sand), Cleavage: None

Formed by the accumulation and cementation of sand-sized grains, typically quartz, with iron oxides (hematite or limonite) acting as the binding agent. Common in Mesozoic or Cenozoic sedimentary basins. The rounded shape suggests fluvial (river) or glacial transport.

Commonly used as construction aggregate or road base when found in large quantities; as a pebble, mainly a collector's curiosity.

The reddish color is due to the oxidation of iron, essentially 'rusting' within the rock layers. The Saratov region (51.5N, 45.9E) is characterized by extensive Cretaceous and Palaeogene sedimentary deposits where such sandstones are common.

Identify by its gritty sandpaper feel and its ability to scratch glass if quartz-heavy. In the Saratov/Volga region, these are ubiquitous in riverbeds and ravines.