John is right, the variation of kg per M3 is very broad, so broad that I question any text that so boldly places a set figure on density for this wood. IMO, this goes for a lot of species not just blackwood. IE: My countrymen and my self are all Australian but we are all quite different even within the same genotypes.
More so than in us humans, environmental influences play a huge part in developing the properties of timber that a individual tree will produce. This is because we, as humans can move freely around and change our environment and diet at will, were as trees can not. {unless of course you live in the 60's, but that is another story
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Aussie blackwood grows from Tasmania, which is cool and has high rain fall, across to Victoria on the mainland, up the coast through New South Wales and into Southern Queensland which is dramatically warmer and dryer when compared to Tasmania.
Maton and many smaller luthiers produce instruments with Blackwood necks. It is fine for this purpose, and is touted to be very stable, just be selective. Generally, if the blackwood is dark, it will be heavier. For necks, look for the lighter coloured timber, the lighter the colour the lighter the neck would be the rule.
As for a source of neck wood, I may have a look around and see, but I do not know any off hand. Most interest of course is directed toward back and side sets and if you play an Aussie Blackwood instrument, you will immediately understand why most luthiers will risk the scratchable itch to sooth the unscratchable itch of the woodaholic.
Cheers
Kim
