This lesson should preface a more in-depth study of the composition of the ocean floor.
Minerals are chemical compounds that occur in the Earth's crust.
Rocks are classified by physical or chemical properties. Some mineral properties include color, luster, hardness, cleavage, and streak. Igneous rock began as another type of rock that was heated, melted, and the cooled into new rock. Sedimentary rocks are made from sediment that was buried, cemented, and them changed to rock. Metamorphic rocks are formed when heat and pressure are applied to rocks in Earth's crust, causing them to change without melting.