Boron, a nonmetallic chemical element never found free in nature. It occurs in various compounds, including boric acid and borax. Pure boron, formed by heating boron compounds with aluminum, appears as transparent crystals, resembling diamonds in brilliance and hardness.

Jeweled bearings and dies for making wire are made of boron carbide, and rocket-powered missiles use boron compounds for fuel. The isotope boron 10 is used to detect neutrons. Nuclear reactions can be controlled by boron-steel rods. Traces of boron in soil seem to play a part in normal growth of plants. The element was isolated in 1808 by the French chemists Joseph Louis Gay-Lussac and Louis Thnard and by Sir Humphry Davy of England.

Symbol: B. Atomic number: 5. Atomic weight: 10.81. Specific gravity: 2.34. Hardness: 9.5. Melting point: about 4,170 F. (2,300 C.). Boiling point: 4,622 F. (2,550 C.). Boron has six known isotopes, of which B-10 and B-11 are stable and occur in nature. Boron belongs to Group III-A of the Periodic Table and has a valence of +3.