sounds like a difficult question to answer cause this is the info I was asking for quite a while back. I was just informed "just pool filter sand" cause it's dustless. I'm now really really really thankful I didn't get the wrong stuff.
I picked up 3 50lb bags of #20 mesh pool filter sand it says it is silica sand. it is brown in color and was $11.00 for a 50 lb bag, i hope this is the right stuff.