What is argillaceous schist or slate; clay slate. Its colors is bluish or blackish gray, sometimes greenish gray, brownish red, etc. -- Ar`gil*lit"ic, a called?

argillite — Argillaceous schist or slate; clay slate. Its colors is bluish or blackish gray, sometimes greenish gray, brownish red, etc. -- Ar`gil*lit"ic, a. (Webster's 1913.)

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