Mudstone
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from shale by its lack of fissility.
Read on WikipediaDried riverbed, compacted into a warm, earthy stone.
Mudstone is a warm grey, close to green.
It can be described as warm, muted, greyish and dusty.
Set in black, because black reads best on it.
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from shale by its lack of fissility.
Read on WikipediaNoun