Ferruginous Sandstone (Gozzanous)

Physical Properties

Hardness: 6-7 (quartz grains) with softer matrix; Color: Rusty brown, reddish, orange, and tan; Luster: Dull to earthy; Texture: Granular/clastic; Specific Gravity: 2.6 - 3.2 (varies with iron content).

Formation & Geological History

Formed through the cementation of sand-sized grains by iron oxide minerals precipitated from groundwater, or via the oxidation and weathering of iron-rich minerals in an existing sandstone unit.

Uses & Applications

Used primarily as low-grade building stone, road fill, or as a source of iron pigments (ochre). It is a significant indicator for geologists looking for metallic ore deposits (gossan mapping).

Geological Facts

Rocks with this high level of iron staining are often called 'ironstone.' They can sometimes contain fossils that have been preserved through mineralization by iron oxides, known as 'limonitic replacement.'

Field Identification & Locations

Identify in the field by checking for high density relative to regular sandstone, a rusty streak (yellowish-brown to red) when scraped, and its characteristic grainy texture that sandpaper-like to the touch. Commonly found in oxidized zones of mineral deposits.

Identified on: 4/25/2026

Mode: Standard