grapholite

From grapho- +‎ -lite, from Ancient Greek γράφειν (gráphein, “writε”) and λίθος (líthos, “stone”).

grapholite (countable and uncountable, plural grapholites)

1. Any variety of slate suitable to be written on.

   grapholite chalkboards

• “grapholite”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.