There are a few main procedures used for classifying different rocks. A few of these are color, streak test, magnetivity, and density. There are many different colors of rocks.
Color is one of the most widely used processes of determining the classification of rocks.
Some rocks are all one color and some contain many different colors Streak tests are another way of classifying different rocks. When you do a streak test you use a porcelain streak plate and the rock that you are trying to classify. By rubbing the rock against the plate it should leave a colored streak on the plate. You can classify the rock by the color of the streak that the rock left on the plate. Some rocks have a magnetic quality.