METHOD OF PREPARING SYNTHETIC MATERIAL WITH NOBLE OPAL STRUCTURE Russian patent published in 2001 - IPC

FIELD: jewelry. SUBSTANCE: monodisperse suspension with amorphous silica of 140 to 600 nm in particle size is first prepared and then subjected to layer precipitation. Precipitate is dried first at 100-150 C for 10 to 30 h and then at reduced pressure (1-10 Pa). Dry precipitate is subjected to pneumatolytic annealing at 350-400 C and pressure 15-45 MPa in presence of water and tetraethoxysilane vapors, impregnated with silica sol, and thermally treated at 400-600 C for 1-2 h. EFFECT: achieved structure of noble opal approaching to a greatest degree to natural opal regarding its jewelry characteristics. 2 ex