Thermite is most commonly made with red iron oxide (hematite, or common rust), but I went with black iron oxide (magnetite) because it should yield more metal per reaction. The ratio for this is 3.22:1 Fe3O4:Al by weight.
Full reaction: 8Al + 3Fe3O4 -> 9Fe + 4Al2O3
This reaction is 40g total, and used my old aluminum powder which was much more coarse (100 mesh vs 425 mesh used in the manganese thermite in my previous post). Look at the size of this reaction compared that one, and that should give you a rough idea of the difference particle size makes. Both are the same total amount of thermite. Check out the last picture and you can clearly see a lump of iron metal sitting on top of the reaction products. There was a larger piece down in the middle of it, and I was able to recover about 7g of good pieces of solid iron for my element collection.