from
The Collaborative International Dictionary of English v.0.48
Slaty \Slat"y\, a. [From {Slate}.]
Resembling slate; having the nature, appearance, or
properties, of slate; composed of thin parallel plates,
capable of being separated by splitting; as, a slaty color or
texture.
[1913 Webster]
{Slaty cleavage} (Min.), cleavage, as of rocks, into thin
leaves or plates, like those of slate; -- applied
especially to those cases in which the planes of cleavage
are not parallel to the planes of stratification. It is
now believed to be caused by the compression which the
strata have undergone.
{Slaty gneiss} (Min.), a variety of gneiss in which the
scales of mica or crystals of hornblende, which are
usually minute, form thin laminae, rendering the rock
easily cleavable.
[1913 Webster]