Chlorite slate

from The Collaborative International Dictionary of English v.0.48

Chlorite \Chlo"rite\, n. [Gr. ? (sc. ?), fr. chlwro`s light
   green.] (Min.)
   The name of a group of minerals, usually of a green color and
   micaceous to granular in structure. They are hydrous
   silicates of alumina, iron, and magnesia.
   [1913 Webster]

   {Chlorite slate}, a schistose or slaty rock consisting of
      alumina, iron, and magnesia.
      [1913 Webster]