where is iridium found
iridium (symbol Ir) Silver-white, metallic element discovered in 1804 by the English chemist Smithson Tennant. A platinum-type metal, iridium is hard and brittle and the most corrosion-resistant metal. very rare element (0.0001 ppm of Earth 's crust), iridium is found in the naturally occurring alloys osmiridium (approximately 50% iridium) and iridiosmium (approximately 70% iridium) in Alaska and South Africa. It is obtained by igniting ammonium chloroiridate, (NH 4) 3 IrCl 6, in hydrogen atmosphere.