I tried a method posted by another user here where to achieve a dispersed refraction/caustics effect, you look up the refractive index of red, green and blue for a material. In this case I just estimated with 2.40 for red, 2.42 for green and 2.44 for blue for diamond, and then I blended the layers with the 'add' mode and blurred each layer a little for firefly suppressing, because I used a relatively low pass count of 150 (because hey, it's a test). The result looks super cool, so I thought I'd share!
