Granite is a naturally found stone composed of several large mineral grains tightly packed together. The main components include Feldspar and Quartz with a mix of other minerals including Biotite and Muscovite.
The minerals Feldspar and Quartz, which are the major components of granite, are harder than steel. This is why throughout human civilization, granite has been used as a building material.
The mica minerals called Biotite and Muscovite are more minor components of granite and give it a glittery appearance.
Compare granite to quartz here.