Synthetic diamond is diamond produced in a technological process, as opposed to natural diamond which is created in geological processes. Numerous claims of diamond synthesis were documented between 1879 and 1928; every attempt has been carefully analyzed and none has been confirmed. In the 1940s, systematic research began in the United States, Sweden and the Soviet Union to grow diamond using chemical vapor deposition (CVD) and high-pressure high-temperature synthesis (HPHT) processes. The first reproducible synthesis was reported around 1953. Those two processes still dominate the production of synthetic diamond. The properties of synthetic diamond depend on the details of the manufacturing processes, and can be inferior or superior to those of natural diamond; the hardness, thermal conductivity and electron mobility are superior in some synthetic diamonds. Consequently, synthetic diamond is widely used in abrasives, cutting and polishing tools and in heat sinks. Electronic applications of synthetic diamond are being developed, including high-power switches at power stations, high-frequency field-effect transistors and light-emitting diodes. Both CVD and HPHT diamonds can be cut into gems and various colors can be produced: clear white, yellow, brown, blue, green and orange.