Tungsten, also called wolfram, is a chemical element that has the symbol W (German: Wolfram) and atomic number 74. A very hard, heavy, steel-gray to white transition metal, tungsten is found in several ores including wolframite and scheelite and is remarkable for its robust physical properties, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. The pure form is used mainly in electrical applications but its many compounds and alloys are widely used in many applications, most notably in light bulb filaments, in X-ray tubes (as both the filament and target), and in superalloys. Tungsten is the only metal from the third transition series that is known to occur in biomolecules.