Clay slate

(Min.) argillaceous schist; argillite.

See also: Clay

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
The dislocation fill with prevailing clayey matrix is equal to clay slate as a mother rock whilst sandy fills with low clay content equal to the Skalka quartzite.
The area protects a rock outcrop representing the tectonic contact between older underlying clay slates of the Zahofany rock series and younger Skalka quartzites bordering alongside of the most important fault in the Prague territory, the Prague Fault (see Figs.