Main Entry: shale

Pronunciation: \ˈshāl\

Function: noun

Etymology: probably from obsolete or dial. shale scale, shell, from Middle English, from Old English scealu — more at shell

Date: 1747

: a fissile rock that is formed by the consolidation of clay, mud, or silt, has a finely stratified or laminated structure, and is composed of minerals essentially unaltered since deposition

— shal·ey also shaly \ˈshā-lē\ adjective