I have a metal substance that looks like silver. It is not attracted to a magnet. A practical method of removing tarnish from silver is to place the silver in an aluminum pan or on aluminum foil, sprinkle baking soda over it, and pour boiling water over it. I did this and noticed bubbling. I also observed a precipitate. I don't think that the reaction of silver plus sodium bicarbonate plus heat should cause a precipitate. So it it isn't silver, what could it be?