Reflections and refractions must be used (not transparency and specular) and they must obey the Fresnel equations. (Which you don't need to know - it's in the Fresnel_Blend node.)

On the left, the abomination as it loads without modification.

On the right, the way it should look.

I'm going away for the weekend so I'm not going to be able to post, but others should be able to help you find the dozens of threads I've written on this kind of material.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)