Ganister is one of the important type of rocks. If we have to define Ganister in general, A ganister is a hard, fine-grained quartzose sandstone or orthoquartzite which is basically used in the manufacture of silica brick typically used to line furnaces and is a type of sedimentary rocks.. Ganister comes under Sedimentary Rocks. All Sedimentary Rocks have similar properties and formation process. Along with Ganister Definition, know more about the History of Ganister, Etymology of Ganister in next sections.