Your circulatory system consists of your heart, blood vessels and blood, and is responsible for transporting life-giving oxygen throughout your body. When you exercise, your body's need for oxygen increases; the harder you work out, the more oxygen your body demands.
Rocks can be divided into three basic classifications: igneous, sedimentary, and metamorphic. The following tests are used by experts to classify rocks: Hardness Test Minerals are scaled in range from 1 to 10, with 1 being softest and 10 hardest. The method of determining hardness is the scratch test.
