Rocks and the Rock Cycle Recall that any sample of matter is either a pure substance or a mixture of two or more pure substances.
Rocks are mixtures of minerals.
The Rock Cycle p rovides a framework that unifies the types of rocks as well as the processes that create rocks and transform them into each other. The rock cycle begins with m agma , a molten soup of minerals deep in the earth. Magma also contains dissolved gases. Lava is magma that has reached the earth s surface. Minerals crystallize out at different temperatures.