What does the word silica mean?

Usage examples for silica

  1. In this material are the abundant supplies of such plant- food as silica, but, as has been previously stated, their very abundance leads us rightly to disregard them in our thinking. – Crops and Methods for Soil Improvement by Alva Agee
  2. The walls of these spaces are said in some cases to contain a considerable amount of silica. – Freshwater Sponges, Hydroids & Polyzoa by Nelson Annandale