Basic Rock Types

Understanding basic rock types gives you more ideas on how each type of rock is formed and this is a good basic for understanding geology.

Rocks can be classified into three main types which are igneous rocks, sedimentary rocks and metamorphic rocks. Figure 1 shows the relationship between the three main rock types.


Figure 1 – Rock Cycle

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Igneous Rocks

Igneous rocks are the most abundant type of rock on the Earth because it makes up about 70% of all rocks. Minerals such as quartz, plagioclase feldspar, pyroxene and olivine are important types of igneous rocks. Figure 3 illustrates minerals found in common igneous rocks.

Figure 2  – Minerals in Common Igneous Rocks.

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