A nonmetalic element analogous to carbon. It always occurs
   combined in nature, and is artificially obtained in the free state,
   usually as a dark brown amorphous powder, or as a dark crystalline
   substance with a meetallic luster. Its oxide is silica, or common
   quartz, and in this form, or as silicates, it is, next to oxygen, the
   most abundant element of the earth's crust. Silicon is
   characteristically the element of the mineral kingdom, as carbon is of
   the organic world. Symbol Si. Atomic weight 28. Called also silicium.