chances of black sand

[roweanmcroy]

Ok guys what affects one chance of getting black sand well sifting, is it ones mines and mountains is it a bile, or is it the purity of the bolder or does it have to do with the numbers that pop up when your chipping the stone and if so what influnces if anything that number?

[Chiprel]

That number influences hardness of the rubble. Which = hardness of gems.(mines and mountains influences the bonus you get).
As for getting black sand while sifting. I don't think anything influences the ammount you get.