[muhd-stohn] 
| a clayey rock with the texture and composition of shale but little or no lamination. |
| mud·stone (mŭd'stōn') n. A fine-grained, dark gray sedimentary rock, formed from silt and clay and similar to shale but without laminations. |
| mudstone (mŭd'stōn') Pronunciation Key
A fine-grained, dark gray sedimentary rock consisting primarily of compacted and hardened silt and clay, similar to shale but without laminations. The proportions of silt and clay in mudstone are approximately equal. |
mudstone
sedimentarysedimentary rock composed primarily of clay- or silt-sized particles (less than 0.063 mm [0.0025 inch] in diameter); it is not laminated or easily split into thin layers. Some geologists designate as mudstone any similar rock that is blocky or massive; others, however, prefer a broader definition that includes all of the members of the shale group. See also siltstone.
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