(n) 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.iridosmine
{ } 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. [ 1913 Webster ]