Diamond is the Central Plains and some crustal rocks through the crust formed by high temperature and pressure metamorphic

Granite is igneous rock, also called acid crystals plutonic igneous rock is the most widely distributed as a rock of feldspar, quartz and mica, whose composition of silica-based, accounting for about 65% to 75%, rock quality hard dense. Igneous rock is called magma underground lava or volcanic eruption condensation crystallized rock.  cubic boron nitride  content, the nature and content of feldspar determine the nature of the stone. When the silica content of greater than 65%, it belongs to acid rock, this rock CKS feldspar, plagioclase, quartz and other minerals to form the basic crystal, granular structure, known as granite.
However, the diamond is the Central Plains and some crustal rocks through the crust to form a high  abrasive grinding  and pressure metamorphic rocks. Forces to promote the role of crustal rock types of the original qualitative change in the process. Qualitative change refers to the original rock structure, structure and mineral composition changes. After a qualitative change in the formation of a new type of rock called metamorphic rocks. Mainly composed of calcite marble, limestone, serpentine and dolomite. The main components mainly calcium carbonate, about 50% or more. Others include magnesium carbonate, calcium oxide, manganese oxide and silica.