Osmium
Also: Os, Osmiridium
Osmium (Os, atomic number 76) is the densest naturally occurring element on Earth and belongs to the platinum group metals.
Osmium (chemical symbol Os) was isolated in 1803 by English chemist Smithson Tennant from the residue of platinum ores. The name derives from the Greek osme (smell) – raw osmium compounds release the highly toxic osmium tetroxide (OsO₄), which has a characteristic pungent odour. Osmium belongs to the platinum group metals and, with a density of 22.59 g/cm³, is the heaviest naturally occurring element of all – slightly denser even than iridium.
Occurrence and Production
Osmium is one of the rarest elements in the Earth's crust (approx. 0.001 ppb). It occurs almost exclusively as a by-product of platinum group metal refining, mainly from nickel-copper ores in South Africa, Russia and Canada. Pure osmium is separated from the platinum concentrate using a multi-stage separation process known as affinage. Global annual production amounts to just a few tonnes.
Properties
Osmium is a blue-grey lustrous, extremely hard and brittle metal. Its melting point of 3,033 °C is the highest of all platinum group metals. This exceptional hardness and density make it unsuitable for many conventional fabrication processes.
| Property | Osmium | Iridium | Platinum |
|---|---|---|---|
| Density (g/cm³) | 22.59 | 22.56 | 21.45 |
| Melting point (°C) | 3,033 | 2,446 | 1,768 |
| Mohs hardness | 7.0 | 6.5 | 4.3 |
Uses
The technical applications of osmium are confined to niche uses:
- Alloys: Combined with iridium or platinum, it serves as a wear-resistant coating for fountain pen nibs, electrical contacts and surgical instruments.
- Catalysis: OsO₄ is used in organic chemistry as an oxidising agent in fine chemicals production.
- Collector market: Since around 2013, crystalline osmium – so-called "iridised osmium" in hexagonal crystal form – has been marketed as an investment object and gemstone. Suppliers promote it as the rarest and densest tradeable element. Note: Due to the absence of an established secondary market and standardised price discovery (no exchange price like the platinum price), valuation is difficult. This is not investment advice.
Price Formation
Unlike platinum, palladium or rhodium, osmium is not traded on a commodity exchange and has no official spot price. Prices are negotiated bilaterally between dealers; for crystalline osmium, specialised certification bodies exist. The current platinum price and other platinum group metal prices as a reference point can be converted into various weight units using the unit converter.
Key Takeaway
Osmium is the densest element on Earth and an extremely rare platinum group metal with highly specialised industrial applications. Crystalline osmium has attracted interest as a collector's item in recent years, but lacks a standardised exchange market – purchasing decisions require careful due diligence.