Ok not that anybody cares but its not the material that makes up the compound of a diamond that makes its strong. Its the arrangment of the tightly packed atoms that gives diamonds their strength and beauty. Diamonds have many tetrahedrons forming carbon-carbon bonds with each other these are formed by the high pressures and temperatures of many years. Because conditions such as temperature and pressure determine which allotrope of carbon occurs. Graphite is created by heating coke or carbon but has a layered structural lattice with weak Van der Waal forces between the layers. The differnce is all structural, call diamond a metal if you will yet it is a poor conductor of electricity, yet a good conductor of heat. Graphite is a good conductor of both, yet a diamonds melting point is somthing like 3500 degrees celcius, good heat sheild anybody?