Osmium is the densest substance known and the hardest of all platinum group metals (PGMs). It is 10 times harder than platinum itself. Osmium also has a higher melting point than the other platinum group metals.

Osmium's extraordinary qualities allow for its use in a range of applications in which frictional wear must be avoided, including fountain pen nibs, styluses, and instrument pivots. It is often alloyed with other PGMs such as platinum and iridium.
Its conductivity means it can be used as a more effective and durable alternative to gold as plating in electronic products.

Like the other PGMs it is an extremely efficient oxidation catalyst and contributes to the environment through use in fuel cells. This quality is also uniquely applied in forensic science for staining fingerprints and DNA (as osmium tetroxide).