A synthetic microsphere having a low alkali metal oxide content and methods of forming the microsphere and its components are provided. The synthetic microsphere is substantially chemically inert and thus a suitable replacement for natural cenospheres, particularly in caustic environments such as cementitious...http://www.google.com/patents/US7878026?utm_source=gb-gplus-sharePatent US7878026 - Synthetic microspheres and methods of making same
