sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
Hardness: 2-4 (Mohs); Color: Gray, brown, black, with green moss/algae growth; Luster: Dull or earthy; Structure: Fine-grained, no visible crystals or bedding; Specific Gravity: 2.2-2.8
- Hardness
- 2-4 (Mohs)
- Color
- Gray, brown, black, with green moss/algae growth
- Luster
- Dull or earthy
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Physical properties
Hardness: 2-4 (Mohs); Color: Gray, brown, black, with green moss/algae growth; Luster: Dull or earthy; Structure: Fine-grained, no visible crystals or bedding; Specific Gravity: 2.2-2.8
Formation & geological history
Formed from the lithification of mud and clay particles deposited in low-energy environments like lake beds, floodplains, or deep marine basins over millions of years.
Uses & applications
Primarily used as fill material in construction or as a source material for brick making and ceramics. Rarely used for decorative purposes unless metamorphosed.
Geological facts
Mudstone is the most common sedimentary rock on Earth, making up about 65% of all sedimentary rocks found in the crust.
Field identification & locations
Identify by its smooth, fine-grained texture that does not scratch glass and its tendency to break into blocky fragments rather than thin sheets (unlike shale). Common in riverbeds and eroded hillsides.
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