Geologists classify
granite as an igneous rock. The slow cooling and
crystallization of molten material called magma
forms most granite. Magma has the same chemical
composition as granite. It forms from rocks that
melt 16 to 25 miles below the surface of the
continents. These rocks melt at temperatures between
1200 and 1650 F. As the magma rises, it cools. Most
granite magma cools slowly enough to form coarse
crystals and it solidifies below the earth's
surface. Once it is solid, it can then be mined into
slab form.