bagginsbill: I tend to agree with your description - in my simple ruby image you see reflected light from the faces on mainly the left side of the image (the sun shines from that side!) and within the shadow the focused refracted light is visible (but needed longer render time to achieve more definition). The key part of the ruby material is the Index Of Refraction data file that controls all elements of the material. I have a simple diamond rendering at the moment with surface and refracted abberation (rainbow) effects visible. Post it later.

Regarding Poser and diamonds I feel the best results will come from dedicated reflection/ environment maps. I've been messing about all afternoon and I have doubts that Poser can achieve a good degree of realism without much time being used. Always fun to have a go with Poser now and again though!