I understand some players are perturbed to find their new instrument has little bits that can be heard rattling around in the instrument when they shake it. These little shavings are in fact the sign of a hand made instrument. If there are none in the instrument when it is finished (having been vacced out previously), I usually drop in a pinch or two.
These are also available from Stew-Mac in three grades. I use the top quality, though since I don’t use abalone, I have to be careful to pick out any abalone fragments, as these would give the game away.