sedimentary

Argillite / Mudstone

Argillaceous sedimentary rock

AI-generated identification · may be incorrect

Hardness: 2-3 on the Mohs scale. Color: Purplish-red to brownish-red due to iron oxide. Luster: Dull or earthy. Crystal structure: Microcrystalline, composed of clay-sized particles and quartz silt. Cleavage: Poor to moderately well-developed parallel to bedding planes. Specific gravity: 2.2-2.6.

Hardness: 2-3 on the Mohs scale
Color: Purplish-red to brownish-red due to iron oxide
Luster: Dull or earthy

Identified August 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the compaction and lithification of mud, silt, and clay particles accumulated in quiet aquatic environments such as lake bottoms, river floodplains, or marine basins. Geological age varies widely from Precambrian to recent.

Uses & applications

Used primarily in brick and tile manufacturing, cement production, and occasionally carved into ornamental items or pipes by indigenous cultures.

Geological facts

The reddish-purple coloration is characteristic of hematite (iron oxide) acting as a pigment and cementing agent in an oxidizing depositional environment.

Field identification & locations

Found worldwide in sedimentary basins. Identified by its very fine-grained texture, earthy appearance, and lack of visible mineral grains without magnification.