Dolomite is a magnesium/calcium carbonate - it's also slower to dissolve then most carbonates (it typically won't fizz via the acid test very easily)
Cuttlefish bone is just calcium carbonate - CaCO3, basically the same stuff as most limestone, crushed coral, oyster shell, etc.
The main mineral component of bone meal should be apatite - Ca5(PO4)3OH, although there is going to be quite a bit of other organic stuff in the bone meal as well.
If you can't get dolomite, I'd try for some form of calcium carbonate - shells, coral, cuttlefish bones, marble, etc. I believe part of the reason to use dolomite is to give some buffering to the lower substrate levels, and prevent them from going too acidic, as well as supplying Magnesium and Calcium cations for plants to use.
I don't really know anything about azomite, and the wikipedia entry looks a bit unreliable, so I don't really have anything to add as to that.
I'm not sure the apatite in bone meal would work very well for this, and I think the additional organic components might cause some problems.
Last edited by lochaber; 05-01-2013 at 05:19 AM.
Reason: forgot azomite