Iridium(IV) oxide

Iridium(IV) oxide, IrO2, is the only well characterised oxide of iridium. It is a blue black solid. The compound adopts the TiO2, rutile structure, featuring six coordinate iridium and three coordinate oxygen.
It is used with other rare oxides in the coating of anode-electrodes for industrial electrolysis and in microelectrodes for electrophysiology research.
As described by its discoverers, it can be formed by treating the green form of iridium trichloride with oxygen at high temperatures:
A hydrated form is also known.