Natural graphite is a lustrous black carbon mineral, crystallized in the hexagonal system with rhombohedral symmetry.
Flake graphite is opaque, flexible and sectile, and exhibits perfect basal cleavage.
Natural graphite is unctuous and relatively soft with a hardness of 1-2 on the Mohs scale. It has a black streak on glazed porcelain. Graphite is an excellent conductor of heat and electricity and has a high melting temperature of 3,500 degrees Celcius. It is extremely resistant to acid, chemically inert, and highly refractory. Amorphous graphite is a microcrystalline graphite formed by crystallization of the carbon from organic sediments.