Silica \Sil"i*ca\, n. [NL., from L. silex, silics, a flint.]

(Chem.) Silicon dioxide, SiO?. It constitutes ordinary quartz (also opal and tridymite), and is artifically prepared as a very fine, white, tasteless, inodorous powder.

Source: Webster's Revised Unabridged Dictionary (1913)