In a typical preparations; the mineral or gel was powdered and mixed well with 0.5 to 1.5 times its volume of solids barium chloride or barium bromide. Warwe was added in amounts 0.5-1.0 of the total solid volume. The mixture was heated in an autoclave at temnperatures of 180 o to 220 oC, preferably for periods of 2 to 6 days.