Sandstone (Ferruginous)

Hardness: 6-7 (Mohs); Color: Brownish-red to ochre; Luster: Dull/Earthy; Crystal structure: Clastic/Granular; Cleavage: None; Specific Gravity: 2.3-2.6

Formed through the accumulation and compaction of sand-sized mineral grains (mostly quartz). The reddish-brown color indicates the presence of iron oxide (hematite or limonite) acting as a cementing agent. Most specimens date from various eras depending on local stratigraphy.

Used primarily in building construction as a dimension stone, as a source of silica for glass making, or crushed for road base and fill material.

Sandstone preserves a significant portion of Earth's fossil record and contains about 20% of the world's petroleum and natural gas reservoirs within its pore spaces.

Identify by its gritty, sandpaper-like texture and visible sand grains. In the field, look for bedding planes or cross-stratification. It is extremely common in desert and ancient river environments globally.