I too, have always used silica/quartz sand in my tanks without any problems other than the initial diatom bloom, which quickly disappears.
I look at it this way, since roughly 90-95% (give or take a percent) of the ocean's floor is silica/quartz sand and silica/quartz is the most common compound on earth... what's good enough for Mother Nature is good enough for me.
BTW, some of the best live sand on the market (
Tampa Bay Saltwater) is... ... ... guess what??? Silica/quartz based from the Gulf Of Mexico!