By what means can I separate solids from a mixture?

Question:

In Chemistry, I have to separate a mixture of 4 solid substances. I removed a substance (had properties of metal shavings) with a strong metal, so that left me with 3 substances. Then, I identified a substance as salt, so I mixed the remaining mixture with water and filtered it, leaving me with 2 remaining substances and a salt solution. (The salt solution, I'll just leave out on a Petri dish and let the water dissolve.) That left me with a substance that looked like sand and a very, very fine substance. How do I separate these two?

Answers:

Get a very fine screen and sift the finer substance from the sand.