There are too many to list, however information about where it was found, color, hardness, translucency, crystal shape, grain size, whether it is magnetic are all useful. Does it react with acid? For example, you find a rock near a silver mine in the country near Albuquerque, NM. It appears metallic. It is non-magnetic. You can't scratch it with your nail, but you can with a pocketknife. It does not scratch glass. (These last three are all hardness tests). It is black and heavy for its size but when you scratch it you see a silver color. It does not react to a weaker acid. You conclude based on the area it was found, it is not magnetic, it is a soft metal, it is silver in color, you might have silver. You can determine its weight with a scale and you can determine its volume with water and a graduated cylinder. Mass divided by volume will give you density. As you can see, there are many ways to narrow your search, then there are specific tests which will tell you more...if you cannot get conclusive proof, you can ask here, there are many rock hounds to help.