A sodium-calcium-borate compound used as a low and mid-range glaze flux. This is a conglomerate mineral made up primarily of Colemanite, Ulexite and Hectorite.
This material is partially soluble and can flocculate glaze slops. It can help prevent crazing when used in small amounts, and can act somewhat as an opacifier in larger amounts, giving glazes a milky appearance. A standard substitute in glazes calling for Colemanite.