1) Mineral 2) Osmiridium 1) Osmiridium 
• (n.) Alt. of Iridosmium
mineral consisting of an alloy of iridium and a smaller proportion of osmium. It occurs in gold-bearing conglomerates, as at the Witwatersrand in ...
Iridosmine or iridosmium is the native compound of iridium and osmium. It is found in flattened metallic grains of extreme hardness, and is often used for pointing gold pen nibs.
a native alloy of iridium and osmium, usually containing some rhodium, ruthenium, platinum, etc., used esp. for the points of gold pens.