Tungsten is the 58th most abundant element found on Earth. No elemental substance exists in nature. Its main source and ore, the main ore is called wolframite or tungsten tetroxide and a mixture of iron, manganese and tungsten oxide. Tungsten ore (oxide) is mainly found in Russia, China, South America, Thailand and Canada. Tungsten is widely used, the most common being tungsten carbide (WC) cemented carbide. Such cemented carbides are commonly used as durable metals in the metalworking, mining, oil extraction and construction industries. In addition, tungsten filaments are widely used in light bulbs and vacuum tubes. Tungsten is also commonly used as an electrode. Tungsten is very hard and compact, making it ideal for making heavy metal alloys such as chemicalbook armors, heat sinks, and high-density applications such as ballasts, counterweights, and ship and aircraft ballasts. Because tungsten is very compact, darts tend to contain 80% to 97% tungsten. High-speed steel contains tungsten, sometimes 18% tungsten. Superalloys containing tungsten (Hastelloy, Stellite, etc.) for making turbine sheets, durable parts and protective layers. Compounds of tungsten can be used as catalysts.