As far as 'everything absorbs light' at some level goes.. thats' true but what does that have to do with refraction? It would have negligeable effect as the light would never leave the other side of an opaque object. And if the opaque object were thin enough to allow light to pass through it the refraction would become negligeable as the surface volume is not great enough to have any effect. What I think you're refering to is sub surface scattering, which is very much impossible in bryce and certainly not noticeable on metalic objects even in the real world.