iridium

A very dense, hard, and brittle, exceptionally corrosion-resistant, whitish-yellow metallic element occurring in platinum ores and used principally to harden platinum and in high-temperature materials, electrical contacts, and wear-resistant bearings. Atomic number 77; atomic weight 192.22; melting point 2,446°C; boiling point 4,428°C; specific gravity 22.562 (at 20°C); valence 2, 3, 4, 6. cross-reference: Periodic Table.

Chemical symbol, Ir; atomic weight, 193. A metal of silver-white color, belonging to the platinum family, and, so far as known, always present in native platinum.

A rare metallic element of atomic number 77, of the same group as platinum, which it much resembles, being silver-white and indifferent to most corrosive agents, but harder, more brittle, and with a higher melting temperature (2410° C, versus platinum 1772° C). With the exception of osmium, it is the heaviest substance known, its specific gravity being 22.4. Symbol Ir. Atomic weight 192.22.

A metallic chemical element (symbol Ir) with an atomic number of 77.

a heavy brittle metallic element of the platinum group; used in alloys; occurs in natural alloys with platinum or osmium