A little info I came across.
BISMUTH is as heavy as lead .
If you have an aversion to using lead for weights you can use BISMUTH. I'm not sure just who all makes BISMUTH weights but I have seen some coming from England in different shops I have been in at times. BISMUTH is as heavy as lead but doesn't have the toxicity.
Have a read on this
BJ
http://en.wikipedia.org/wiki/Bismuth