Carbon is one of the essential elements of life on Earth. Derived from the Latin: Carbo, which means coal, Carbon has the chemical symbol C. On the periodic table, Carbon is in group 14 period 2. In geology, graphite and Carbon are the two mineral forms of Carbon. They both have the same chemical composition but were formed in very different environments. Hence why diamond has a hardness of 10, and graphite has a hardness of 1.
Diamond forms in the mantle under intense heat and pressure. Most graphite found near Earth's surface was formed within the crust at lower temperatures and pressures. Graphite and diamond share the same composition but have very different structures.
The different environments in which these minerals form define the structure of each mineral. The carbon atoms in graphite are linked in a hexagonal network, which forms sheets that are one atom thick. These sheets are poorly connected and break easily when little force is applied. This gives graphite its very low hardness, its perfect cleavage, and its slippery feel.
In contrast, the carbon atoms within a diamond are arranged tetrahedrally. Every atom is linked into a three-dimensional network with four other carbon atoms with strong covalent bonds. This arrangement holds the atoms firmly in place and makes the diamond hardest mineral.
original on 2017-10-24.