Models of Diamond and Graphite Atoms
Both graphite and diamond are made of carbon. But diamond, with more closely packed atoms, is considerably harder than graphite.
Characteristic physical properties distinguishing each mineral reflect the chemical elements present and, more importantly, their arrangement in its crystal structure. Seen here are the crystal structure of graphite and of diamond, both minerals formed solely of the element carbon. Close packing in all directions of atoms in the diamond explain its great hardness. In graphite, atoms within a plane are closely packed, but much weaker bonding between the planes results in a soft mineral with good cleavage.