Silicon carbide (sic), also known as carborundum, is a compound of silicon and carbon  with chemical formula sic. It occurs in nature as the extremely rare mineral  moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics  that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Electronic applications of silicon carbide as light-emitting diodes (leds) and detectors in early radios were first demonstrated around 1907. Today sic is used in semiconductor electronics applications that are high-temperature, high-voltage or both. Large single crystals of silicon carbide can be grown by the lely method; they can be cut into gems known as synthetic moissanite. Silicon carbide with high surface area can be produced from sio2 contained in plant material.