These two highly profitable operations simply cast off selenium as a byproduct. The most striking feature of selenium is its electrical conductivity. Unlike most electrical conductors, selenium varies in conductivity with variations in light. The conductivity of pure selenium can increase as much as a thousand-times when a sample is taken from darkness into bright sunlight. Selenium can be found in all kinds of light-sensitive devices such as photocells, solar cells, television cameras and light meters.
Selenium is also suitable for use in rectifiers.
Selenium has specialized applications in rubber vulcanization and catalysis and as a colourant in glass and ceramic products.