Diamond is a solid form of carbon with a diamond cubic crystal structure. At room temperature and pressure it is metastable and graphite is the stable form, but diamond almost never converts to graphite. Diamond is renowned for its superlative physical qualities, most of which originate from the strong covalent bonding between its atoms. In particular, it has the highest hardness and thermal conductivity of any bulk material. Those properties determine the major industrial applications of diamond in cutting and polishing tools and the scientific applications in diamond knives and diamond anvil cells.