The 2000 known minerals can form an endless number of combinations and give life to an extremely high number of rocks. The processes that lead to the creation of a rock do not separate the different minerals the rock consists of. As a consequence, it is difficult to find rocks consisting of one single mineral. We will see that rocks are a mixture of different minerals; only those minerals that are present in a higher quantity identify the type of rock. For example granite is a magmatic rock that consists of many minerals, but especially quartz, feldspars and mica are always present in a large quantity.
The process that leads to rock formation is fundamentally important, therefore rocks are classified according to how they were formed:

  • magmatic or igneus rocks derive from the cooling of a mass of minerals in melted state (magma). Those minerals are mixed with gas substances during a process called magmatic process;
  • sedimentary rocks consist of rock fragments that have been accumulated during a process called sedimentary process;
  • metamorphic rocks are rocks that underwent modifications during geologic ages. The process that describes these changes is called metamorphic process.

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