Tungsten is a chemical element with the symbol W and atomic number 74. It is a dense, hard, and gray metal that is also very brittle and difficult to work with. Tungsten has the highest melting point of any metal, at 3422°C (6192°F), and the second-highest boiling point, at 5930°C (10706°F). This makes it an ideal material for high-temperature applications such as light bulb filaments, heating elements, and rocket nozzles. Tungsten is also very dense, with a density of 19.25 grams per cubic centimeter. This makes it useful for applications where a high mass-to-volume ratio is desirable, such as in radiation shielding and kinetic energy penetrators. Tungsten is often alloyed with other metals to improve its properties. One common tungsten alloy is tungsten carbide, which is made by combining tungsten with carbon. Tungsten carbide is extremely hard and is used in cutting tools, abrasives, and jewelry. Tungsten is also used in the production of electrical contacts, as it has a low coefficient of thermal expansion and a high resistance to arc erosion. It is also used as a filament in incandescent light bulbs, although these are becoming increasingly rare due to the rise of more energy-efficient LED lighting. Tungsten is a relatively rare element, with an abundance in the Earth's crust of only about 1.5 parts per million. It is primarily mined in China, Russia, Canada, Bolivia, and Austria. Tungsten has some toxic properties and can cause lung cancer if inhaled as dust or fumes. Therefore, appropriate safety precautions should be taken when working with tungsten.