Boron does not occur naturally as a free element, but in compounds such as borates. The most common sources of boron are tourmaline, borax, Na2B4O5(OH)4·8H2O, and kernite, Na2B4O5(OH)4·2H2O. it is difficult to obtain pure boron. It can be made through the magnesium reduction of boron trioxide, B2O3. This oxide is made by melting boric acid, B(OH)3, which in turn is obtained from borax. Small amounts of pure boron can be made by the thermal decomposition of boron bromide, BBr3, in hydrogen gas over hot tantalum wire, which acts as a catalyst. The most commercially important sources of boron are: sodium tetraborate pentahydrate, Na2B4O7 · 5H2O, which is used in large amounts in making insulating fiberglass and sodium perborate bleach; boron carbide, a ceramic material, is used to make armour materials, especially in bulletproof vests for soldiers and police officers; orthoboric acid, H3BO3 or boric acid, used in the production of textile fiberglass and flat panel displays; sodium tetraborate decahydrate, Na2B4O7 · 10H2O or borax, used in the production of adhesives; and the isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons.