These clays are highly silicious and in composition are intermediate between the Yorkshire fireclays and ganister.
For furnace linings, the quartzite or ganister must be exceptionally pure.
The principal uses of sandstone are for building stone, crushed stone, and ganister (for silica brick and furnace-linings).
After covering all the exposed steel surfaces with ganister, the plates are put in a gas furnace and heated to a welding heat.
Lower: Flaggy hard sandstones (ganister), shales and thin coal seams.