Main Entry:

shale

Pronunciation:

\ˈshāl\

Function:

noun

Etymology:

probably from obsolete or dialect 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