A medium grog added to clay bodies primarily to reduce stress from dry shrinkage. In clays fired above 1100º C, it fires off-white and begins to expand as it converts to mullite, effectively reducing the clay’s fired shrinkage.
With a little clay and sodium silicate, excellent refractory mortars can be made with kyanite.
For more information on kyanite, see the Digitalfire.com Reference Library of ceramic materials.