Igneous means made from fire. Igneous rocks form when magma cools. As it cools, minerals "drop out" and form crystals. These minerals can be either mafic or felsic.
Mafic minerals are dark in color. They are produced at high temperatures. Mafic minerals include olivine and pyroxene. Basalt and gabbro are common mafic rocks.
Felsic minerals are light-colored. They include quartz and mica. The most common felsic rock is granite.
How do all these different minerals and rocks form from the same magma? Geologist Norman Bowen came up with a solution to this puzzle. It is called Bowen's reaction series.
Bowen's reaction series describes how minerals form as magma cools. The temperature of the magma and the rate at which it cools have an effect on the minerals that form. Bowen's reaction series shows how eight common minerals form from the same magma.