I do have some silica sand that I was going to use for building DIY live rock. It doesn't pass the vinegar test and.... there is only about 1/3 of a salt bucket amount. You are welcome to it.
I am going out of town this weekend so if you need it before then we will need to set up something quick. Cell phone = 719-661-7421
BTW, why would you want to use silica sand? As a suggestion, if you are going to put it in your tank, I would use crushed coral as a bottom substrate and then put what Southdown sand on top of that to get the depth you want. In any case, let me know. I work up in Denver these days but can set something up early next week.