The element is not found free in nature, but occurs as orthoboric acid in volcanic spring waters and as borates in borax and colemanite. The most important source of boron is the mineral rasorite, also known as kernite. Symbol, B. Amorphous boron is used in pyrotechnic flares and in rockets as an igniter; the most important compound, boric acid or boracic acid, is used as an antiseptic; borax is used as a cleansing flux in welding and as a water softener. The isotope boron-10 is used in nuclear reactors; the nitride has lubricating properties similar to those of graphite; and the hydrides have been studied for use as rocket fuels.