Osmium has the highest melting point among the platinum-group metals.
Its melting point is about 3,033°C, higher than iridium’s roughly 2,446°C and platinum’s roughly 1,768°C. The platinum-group metals also include ruthenium, rhodium and palladium. Osmium’s strong metallic bonding helps explain its resistance to heat, but the metal is extremely hard and brittle, making it difficult to shape.
Osmium was discovered in London in 1803 by Smithson Tennant and William Hyde Wollaston while investigating the dark residue left after dissolving platinum ore. Its name comes from the Greek word osme, meaning “smell,” because osmium tetroxide has a powerful odor.
A common mix-up is confusing melting point with density. Osmium is also the densest stable element, at about 22.587 g/cm³, but that is a different property. Osmium tetroxide is volatile and highly toxic, so osmium compounds—not ordinary jewelry metal—are the main safety concern.