Material properties of diamond to a very large kinetic energy barrier, diamonds are metastable; they will not decay into graphite under normal conditions. Material properties of diamond Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is an optically isotropic crystal that is transparent to opaque. Diamond is the hardest naturally occurring material known. Yet, due to important structural weaknesses, diamond's toughness is only fair to good. The precise tensile strength of diamond is unknown, however strength up to 60 GPa has been observed, and it could be as
Mineral is in six-fold coordination; its chemical formula can be expressed as AlAlSiO, to reflect its crystal structure. Andalusite has the second aluminium in five-fold coordination (AlAlSiO) and sillimanite has it in four-fold coordination (AlAlSiO). Differences in crystal structure and chemistry greatly influence other physical properties of the mineral. The carbon allotropes diamond and graphite have vastly different properties; diamond is the hardest natural substance, has an adamantine lustre, and belongs to the isometric crystal family, whereas graphite is very soft, has a greasy lustre, and crystallises in the hexagonal family. This difference is accounted for by differences in bonding. In