In mineralogy, diamond (from the ancient Greek adámas) is the allotrope of carbon, where the carbon atoms are arranged in a variation of the face centered cubic crystal structure called diamond lattice. After graphite, diamond is the second most stable form of carbon. Its hardness and high dispersion of light make it useful for industrial applications and jewelry. It is the hardest known mineral. It is possible to treat regular diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in hardness gauges.