sedimentary

Pyritic Shale

Carbonaceous Shale with Iron Pyrite (FeS2)

AI-generated identification · may be incorrect

Hardness: 3-4 (matrix) to 6-6.5 (pyrite), Color: Black/dark grey with metallic brassy-yellow inclusions, Luster: Dull/earthy matrix with metallic inclusions, Crystal structure: Isometric (pyrite cubes or grains), Specific gravity: ~2.6-5.0

Hardness: 3-4 (matrix) to 6-6

Identified June 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in low-oxygen, organic-rich marine or lacustrine environments where sulfate-reducing bacteria react with iron and organic matter. Often associated with Devonian or Pennsylvanian age strata.

Uses & applications

Historically used for sulfuric acid production; scientifically important for understanding paleo-environments; used in educational collections and as a source for fossil hunting.

Geological facts

Also known as 'Fool\'s Gold' in shale. The pyrite specifically forms through the biological reduction of seawater sulfate. These rocks are often fossiliferous, containing well-preserved carbonized remains.

Field identification & locations

Identify by its dark fissile (layering) nature and the brassy metallic glint of the pyrite. Common in coal-bearing regions and ancient sea beds. Be wary of 'pyrite disease' where the sulfur reacts with humidity to decay the specimen.