Reply by sparks

Have you put a finish back over the project yet. When I did turquoise it looked white and opaque but when I but the clear finish over it, it looked great. Even an oil finish over it should help. The turquoise was quite dull after I sanded it smooth but as soon as the finish went on it really brought out all the colors. I also used some black crushed garnet in a table top knot and same thing and that finish was 1/3 boiled linseed oil, 1/3 spirits, 1/3 gloss varnish and looked great when done. I think you should try a finish over it and hopefully fixes your problem.

-- Sparks