Tungsten carbide (WC) is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery, tools, abrasives, as well as jewelry. Tungsten carbide is approximately three times stiffer than steel, with a Young's modulus of approximately 550 GPa,[2] and is much denser than steel or titanium. It is comparable with corundum Structure α-WC structure, carbon atoms are gray.[1] There are two forms of WC, a hexagonal form, α-WC (hP2, space group P6m2, No. 187),[1][11] and a cubic high-temperature form, β-WC, which has the rock salt structure.[12] The hexagonal form can be visualized as made up of hexagonally close packed layers of metal atoms with layers lying directly over one another, with carbon atoms filling half the interstices giving both tungsten and carbon a regular trigonal prismatic, 6 coordination.[11] From the unit cell dimensions[13] the following bond lengths can be determined; the distance between the tungsten atoms in a hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The tungsten-carbon bond length is therefore comparable to the single bond in W(CH3)6 (218 pm) in which there is strongly distorted trigonal prismatic coordination of tungsten.[14] Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for 184W12C.[15]