The Collaborative International Dictionary of English v.0.48:

Ganister \Gan"is*ter\, Gannister \Gan"nis*ter\, n. (Mech.)
   A refractory material consisting of crushed or ground
   siliceous stone, mixed with fire clay; -- used for lining
   Bessemer converters; also used for macadamizing roads.
   [1913 Webster]