US Patent 7465421 Process of preparation of synthetic fire opal

A synthetic fire opal and a process for its preparation. Synthetic fire opals have similar physical and chemical properties as natural fire opals. Synthetic fire opals are colored, hard, and transparent. The process of preparation of synthetic fire opal includes; mixing TEOS with absolute ethanol (99.9%), distilled water, concentrated nitric acid, and an inorganic salt to form a clear sol, storing the clear sol to obtain a gel, drying the gel and sintering the dried gel to obtain a synthetic fire opal.