QuoteIndex of refraction... Nice tip.
Yes, it is. Matt enlightened us to this little biscuit a while back for using the reflective shader. Before, I'd have just upped the reflectivity factor beyond '1' for a more shiny feel. That way, though, seems to be where the black(are they improperly calculated reflected reflections?) parts come from in a lot of shiny renders, when using higher reflective values than 1.
Upping the refraction index significantly can give you some beautiful chrome/metal/mirror effects.
In this linked render of a saucer(made of TG rocks and discs)
http://forums.planetside.co.uk/index.php?topic=5312.0 I think my chrome shaders were about IOR=8 or 10.
I've seen me using values of 20-30.
Always remember a slider is only a slider if you slide it! Try inputing values manually, every field in TG can be forced well past the slider's limits...
I did have a table of indeces of refraction for common crystal/stones/etc, I seem to have lost it now, Google for a table to check indeces yourself. I think the highest scale in it, though, was 2.4(something) for diamond.