Kirado shares a technique to simulate dispersion with Cycles.
Diamonds rendered in Blender Cycles, using a faked dispersion shader.
I made a diamond shader a few months back; after seeing some diamond renders appearing here on Blendernation I thought I should share the node tree, so people can see what's possible with cycles, and get the most out of their jewellery renders.
I did a mental ray diamond tutorial ages ago on Zaps Mental Ray Blog and wanted to see if I could get similar dispersion shader working in Cycles. The Diamonds were modelled in 3ds Max and imported into Blender.
I only used RGB Shaders with slighty different IOR mixed with ADD.
Would be fantastic if someone could hard-code a dispersion setting into the glass node ;-)