sedimentary

Red Sandstone with Reduction Spot

Quartzose Sandstone with a Leach/Reduction Spot

Hardness: 6-7 on the Mohs scale (due to quartz grains); Color: Reddish-brown with a lighter pale/greenish reduction spot (often called a 'leopard spot' or 'green spot') featuring a dark center; Luster: Dull to earthy; Crystal structure: Clastic/granular texture composed of microscopic quartz crystals;…

Hardness: 6-7 on the Mohs scale (due to quartz grains)
Luster: Dull to earthy

Identified July 30, 2026More sedimentary →

Explore Red Sandstone with Reduction Spot in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the accumulation, compaction, and cementation of mineral particles or rock fragments (predominantly quartz) in ancient desert, river, or marine environments, typically during the Paleozoic or Mesozoic eras. The distinctive spot is formed post-depositionally when iron oxides (hematite) are chemically reduced or leached out by organic matter or localized chemical reactions.

Uses & applications

Used primarily in educational geology collections, as a decorative stone, and historically as a building and paving material.

Geological facts

The contrasting spots in red beds are often referred to as reduction spots or coloration reduction features. They frequently form around tiny organic nuclei, such as a microscopic piece of plant matter or a fossil fragment, which locally alters the chemical environment and leaches the red iron coloration.

Field identification & locations

Easily identified by its reddish matrix containing distinctive circular lighter halos, often with a dark nucleus at the center. Commonly found in sedimentary basins worldwide where ancient red-bed sandstones are exposed.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Sedimentary Sandstone

Arenite (Sedimentary Rock)

sedimentary

Fossiliferous Concretion

Septarian Concretion containing Brachiopods/Crinoids

fossil

Banded Siltstone / Mudstone Pebble

Siltstone / Argillite

sedimentary

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)

sedimentary

Shale

Shale (clastic sedimentary rock)

sedimentary