Sandstone (Ferruginous)

Physical Properties

Hardness: 6-7 on Mohs scale (depending on cementing material); Color: Reddish-brown, tan, and gray due to iron oxidation; Luster: Dull to earthy; Crystal structure: Clastic (grains of quartz); Cleavage: None; Specific Gravity: 2.2–2.8.

Formation & Geological History

Formed through the accumulation and litification of sand-sized mineral grains or rock fragments. The reddish hue indicates an oxygen-rich environment where iron minerals (like hematite or goethite) oxidized during or after the deposition process.

Uses & Applications

Commonly used as a building material, in road construction (aggregate), and for landscaping. Higher purity quartz sandstones are used in glass manufacturing.

Geological Facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The red color in famous landscapes like the Grand Canyon or Sedona is primarily due to iron-oxide-rich sandstone similar to this specimen.

Field Identification & Locations

Identify by its 'sandpaper' feel and visible layers (bedding planes). When wet, as seen in the lower half of the image, the colors become more vibrant. Often found in riverbeds, canyons, and coastal bluffs.

Identified on: 4/27/2026

Mode: Standard