osmiridium

Osmiridium is a natural alloy of osmium and iridium, two platinum-group metals. It occurs as irregular grains or masses within platinum-bearing ores and in placers, often alongside other platinum-group metals such as platinum, palladium, ruthenium, and rhodium. It has a very high density, about 22.5 g/cm3, and a metallic luster; its color ranges from bluish-silver to dark gray.

The term osmiridium is sometimes used to describe osmium-rich alloys; iridosmine is the iridium-rich counterpart. The two forms were historically distinguished by their relative osmium and iridium content.

Osmiridium is a minor natural occurrence worldwide, with deposits reported in platinum-bearing regions such as South Africa, Russia, and Canada. It is not a practical ore for widespread industrial use due to its rarity and the difficulty of separating osmium and iridium, but it is processed to recover the constituent metals as separate elements.

In summary, osmiridium refers to the natural Os–Ir alloy found within platinum-group mineral assemblages. It is notable for its extreme density and rarity and is primarily of mineralogical and metallurgical interest, rather than as a bulk ore source.