Iridium
Also: Ir, Iridium metal
Iridium (Ir) is a silver-white platinum-group precious metal with one of the highest densities of all elements (22.56 g/cm³, just behind osmium) and exceptional corrosion resistance.
Iridium belongs to the group of platinum-group metals and is considered one of the rarest and most difficult-to-process metals on Earth. With a density of 22.56 g/cm³, it is the second densest naturally occurring element — just behind the related osmium (22.59 g/cm³). It was discovered in 1803 by Smithson Tennant, who named it after the Greek goddess Iris (rainbow) because its salts appear in strikingly different colours.
Occurrence and Extraction
Iridium occurs in the Earth's crust at concentrations of approximately 0.001 ppb — about ten times rarer than gold. It is extracted almost exclusively as a by-product of nickel and copper production from platinum ores, predominantly in South Africa (Bushveld Complex), Russia and Zimbabwe. Global annual production fluctuates between seven and nine tonnes, making it significantly lower than that of platinum or palladium.
Properties
The technical characteristics of iridium are exceptional:
- Highest corrosion resistance of all metals: iridium dissolves neither in hydrochloric acid nor in sulphuric acid. Only aqua regia attacks it under certain conditions.
- Extremely high melting point of 2,446 °C — higher than almost all technically usable metals.
- High hardness (Mohs 6.5) combined with pronounced brittleness, which makes mechanical processing considerably more difficult.
Industrial Applications
Due to its resistance, iridium is used in high-temperature and high-precision applications:
| Sector | Application |
|---|---|
| Automotive | Spark plug electrodes (Ir alloy) |
| Chemistry | Crucible material for single-crystal growth |
| Medicine | Radiation therapy (Ir-192 implants) |
| Aerospace | Rocket engines, heat shielding |
| Metrology | Historical: kilogram prototype alloy (Pt-10%Ir) |
Iridium as an Investment and Trading Asset
In contrast to gold, silver, platinum or palladium, there is no established futures market (COMEX) and no daily fixing for iridium. Prices are published as indicative prices by industrial wholesalers such as Johnson Matthey or Heraeus. The extreme tightness of the market — a few tonnes of annual production, a few major buyers — leads to sometimes strong price fluctuations at low trading volumes. Iridium is primarily an industrial metal; liquid investment products (coins, ETCs) are barely available. Comparable historical price trends of platinum-group metals can be tracked on the platform.
Tax and investment advice regarding iridium as an investment object must be assessed individually — this entry does not constitute tax or investment advice.
In Brief
Iridium is the densest and most corrosion-resistant metal on Earth, occurring almost exclusively as a by-product of platinum mining, and is considered primarily an industrial metal due to its extreme rarity and the absence of liquid trading markets. Current prices of related platinum-group metals provide orientation for the price level of this market segment.