If you want to add shimmer to your jewelry, get the PixieCrafting gemstone pigments. These pigments give your resin an iridescent, iridescent look. You should work them into the resin along with the normal pigments. Please note that adding pigment will increase the resin's curing time slightly.
You will receive 5x10ml Gemstone Pigment in a sealed vial. Cut off the very tip of the spray nozzle and you're good to go