Iridium is the second densest of all elements. With a melting temperature of 2446°C (4435°F), it is exceeded only by the refractory group metals. It exhibits excellent high temperature properties and mechanical strength, being used in certain applications, unprotected, in air at temperatures exceeding 2000°C (3632°F). At these temperatures it also shows outstanding resistance to a variety of salts and oxides. It is unaffected by common mineral acids and aqua regia.

This makes iridium an obvious choice for a whole range of high temperature applications.

However, its high degree of stiffness and resistance to deformation render its fabrication into complex components difficult.

Johnson Matthey has spent many years developing an understanding of the methods of working iridium into component form.

The installation of specialty melting equipment, hot rolling and drawing plant, and thermal deposition systems in our facilities at Royston near Cambridge in the UK, and at West Chester near Philadelphia in the USA, has resulted in a unique fabrication ability in iridium.

Crystal growing

Johnson Matthey has extensive experience and expertise in manufacturing Iridium crucibles for crystal growth in a wide range of industries.


Johnson Matthey has capabilities to manufacture other bespoke Iridium fabrications for use in a variety of industries where temperature is a critical factor.


Johnson Matthey manufactures Iridium wire and ribbon which is used widely in filaments. Iridium’s strength and chemical resistance makes it the ideal material for filaments.

Spark plugs

Johnson Matthey has vast experience in the manufacture Platinum, Iridium and alloys used in the production of premium grade spark plugs producers in the automotive industry, which give the spark plugs up to 100,000 miles usage.

Iridium has a melting point of 2,446°C which makes it a perfect choice for use in even more demanding spark plug applications

More stringent emission standards and a more demanding engine environment, including increased service intervals, have led to a requirement for spark plug alloys with even better properties.

Mechanical properties (20°C)

Alloy System Alloy Condition UTS MPa Strain % Hardness HV
Iridium Pure Hot Worked 1,730 16 486
Recrystalised 740 14 240
Rhodium / Iridium 5% Rh/Ir Hot Worked 1,730 11 550
Recrystalised 500 7 260
10% Rh/Ir Hot Worked 1,840 10 595
Recrystalised 590 6 280
40% Rh/Ir Hot Worked 1,855 13 492
Recrystalised 673 8 268
Platinum / Iridium 5% Pt/Ir Hot Worked 2,456 13 596
Recrystalised 710 4.5 350