Sandstone (Ferruginous)

Physical Properties

Hardness: 6-7 (Mohs scale), Color: Reddish-brown, tan, and gray, Luster: Dull/Earthy, Crystal Structure: Granular/Clastic, Cleavage: None, Specific Gravity: 2.2-2.8

Formation & Geological History

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments, primarily quartz. The reddish tint indicates the presence of iron oxide (hematite or limonite) acting as a cementing agent. Geological age varies from Precambrian to Cenozoic.

Uses & Applications

Used primarily in construction as a building stone or paving material. Crushed sandstone is used in road bases and glass manufacturing if quartz purity is high.

Geological Facts

Sandstone represents about 20% of all sedimentary rocks on Earth. The iron oxide that gives this specimen its red color is the same mineral responsible for the color of the red rocks in Sedona, Arizona.

Field Identification & Locations

Identify in the field by its gritty, abrasive feel (like sandpaper) and visible sand grains. Commonly found in river beds, deserts, and coastal areas. Collectors look for unique banding or iron concretions.

Identified on: 5/3/2026

Mode: Standard