Osmium is an extremely rare and expensive transition metal, and only a few hundred kilograms are produced annually.
It is the densest chemical element, and rivals diamond as being the least compressible of all known substances.
It doesn’t have many uses, although its hardness makes it useful in fountain pen nibs and clock bearings.
The name osmium comes from the Grek osme, meaning ‘smell’. Osmium tetroxide has a distinctive 'pong' according to Allan Blackman, in ep 55 of Elemental.
The Elemental podcast is celebrating 150 years since the periodic table was first published by Russian chemist Dmitri Mendeleev.
Find out more about events during the United Nation’s International Year of the Periodic Table.
Professor Allan Blackman is at Auckland University of Technology.