Osmiridium

Osmiridium and iridosmine are natural alloys of the elements osmium and iridium, with traces of other platinum-group metals.

One very productive mine was operated at Adamsfield near Tyenna in Tasmania during the Second World War with the ore shipped out by railway from Maydena.

It was once one of the world's major producers of this rare metal, and the osmiridium was mostly found in shallow alluvial workings.

[citation needed] It can be isolated by adding a piece to aqua regia, which has the ability to dissolve gold and platinum but not osmiridium.

It occurs naturally as small, extremely hard, flat metallic grains with hexagonal crystal structure.