A nonmetallic element occurring abundantly in borax. It is
   reduced with difficulty to the free state, when it can be obtained in
   several different forms; viz., as a substance of a deep olive color, in
   a semimetallic form, and in colorless quadratic crystals similar to the
   diamond in hardness and other properties. It occurs in nature also in
   boracite, datolite, tourmaline, and some other minerals. Atomic weight
   10.9. Symbol B.