This is a discussion on nepheline syenite within the Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; -->
i kno on my old forum they had a list of rocks that are aquarium friendly.
i just got a silica sand made of ...
Probabaly not safe to use unless you are in need of really hard water. A lot of that is greek to me too (I assume you tried to parse the Wikipedia Entry), but Alkali Feldspar is going to leech Calcium into your water, raising the hardness and PH. Now, if you're doing livebearers or Rift Lake or Central American cichlids or brackish water fish or desert gobies, you'll be fine. If you're doing anything like Cories or Loaches or Pleco or Tetras or Anabantids, or anything that likes soft, acid water, not so fine.
If that's a 33 long, that could be an awesome tank with lake Tanganyika shell dwellers. Otherwise, you could do a really neat North or Central American tank. A male and 4 female sailfin mollies, a Firemouth or 2, and an American-Flag Fish or two. You could plant that second option with Vals and Java Moss and Java Fern and hormwort - all do great in hard water. So does Mexican Oakleaf.
Your best bet is really to find fish that work with the conditions you're setting up.
i actually have a ten gallon i can use for those! sites say 6 can go in as juvs, but idk about adult size.
Adult size is up to 6" for some species of Male Sailfin Molly (I think it's P. velifera that gets big) - More likely 4" (what you'll see in pet stores is a hybrid of P. latipinna and others). If you get a male and a harem for him, they will fill a tank of any size you care to name, given time and places for the fry to get out of the way. 10 gallons is too small for anything but a temporary breeding or grow out tank.
Still, if you want to use that sand, hard water fish remain your best choice. Someone else can tell you about rift lake cichlids. They might be the way to go for you.