n 1: a hard and corrosion resistant mineral that is a natural alloy of osmium and iridium (usually containing small amounts of rhodium and platinum); used in needles and pen nibs etc. [syn: osmiridium, iridosmine]
Iridosmine Ir`i*dos"mine, Iridosmium Ir`i*dos"mi*um, n. [Iridium + osmium.] (Min.) The native compound of iridium and osmium. It is found in flattened metallic grains of extreme hardness, and is often used for pointing gold pens.