Igneous Rock Classification

The most common igneous rocks are classified using just two characteristics: Crystal size and color. For example, basalt is relatively dark in color (gray to black) and usually contains crystals to small to see without the aid of an optical lens. 

On the other hand, granites are lighter in color (pink to gray) and have crystals that can be seen by the naked eye. 

Igneous rocks are the only kind of rock that forms from hot magma, and all rock that crystallize from melted rock are igneous.  

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