1. a fine-grained sedimentary rock formed from compressed mud and clay
Usage: geology

Examples

• The geologist identified layers of mudstone in the cliff face.
• Mudstone forms when fine particles of mud are compressed over millions of years.
• The fossil was perfectly preserved in the mudstone.
• Oil companies often drill through mudstone to reach deeper rock formations.
• The red mudstone indicated an ancient lake bed.
• Mudstone is softer than sandstone and breaks apart more easily.