Get a magnet, if it sticks it goes in one pile if it don't put it in another pile. You said you know how to tell copper, so obviously that goes in a pile of its own. Next is brass, aluminum and stainless steel. Brass will be of simular color of copper but brittle and break when you hit it several times with a hammer. Aluminum and stainless to some are difficult to tell apart, aluminum and stainless are both silvery white metals, ali can be cast, sheet or extruded, all will be easy to scratch with a screw driver, stainless is usually in sheet form but not always and will not scratch easily with a screwdriver. First and formost, get a magnet.
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