They combine to form quartz, one of the most abundant of the minerals. A different combination of elements produces the mineral feldspar. Scientists know about 1,500 minerals. The only ones that occur in large enough masses to be important as rock builders, however, are quartz, feldspar, and a group called the ferromagnesian minerals. They are dark because they contain iron and magnesium.
Granite is an igneous rock.
Rock Igneous rocks are still being formed from pockets of magma some 40 miles underground. Magma is a hot, doughy material mixed with gases and steam. It rises along cracks in the Earth's crust. If it solidifies before it reaches the surface it forms an intrusive igneous rock. If it is thrown out by volcanic action, it forms an extrusive igneous rock.