Tungsten is a metallic element that has the symbol W and the atomic number 74. It is also called Wofram from which the symbol results. It is a very hard, heavy, steel-gray to white bittle transition metal and is found in several ores primarily wolframite and sheelite. It is remarkable for its unique physical properties. It has the highest melting point of all the non-alloyed metals. The metal is used mainly in electrical applications such as light bulbs, but also in cutting and wear resistant materials. Its compounds and alloys are widely used in many applications such as in X-ray tubes (as both the filament and the target), and in super alloys. It is also used extensively in petroleum refining as a hydrocracking catalyst and in the removal of sulfur and nitrogen.