The Collaborative International Dictionary of English v.0.48:

Silicon \Sil"i*con\, n. [See Silica.] (Chem.)
   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.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Silicium \Si*lic"i*um\, n.
   See Silicon.
   [1913 Webster]