A History Of Iridium

Posted on by Brian Colwell

Iridium, the second-densest naturally occurring metal on Earth, has captivated scientists and engineers since its discovery over two centuries ago. Named after the Greek goddess Iris for the rainbow of colors its compounds display, this remarkable element has journeyed from laboratory curiosity to industrial catalyst, from fountain pen tips to spacecraft components. This silvery-white transition metal, with its extraordinary resistance to corrosion and ability to withstand temperatures exceeding 2,000°C, has played pivotal roles in defining mass standards, enabling chemical processes, illuminating displays, and even helping scientists understand the extinction of dinosaurs. The story of iridium is one of scientific discovery, technological innovation, and industrial transformation spanning more than two hundred years.

Read about the six platinum group metals – Iridium, Osmium, Palladium, Platinum, Rhodium, and Ruthenium – as a group (PGMs) here. Find out about the other critical raw materials (CRMs) here. The complete history of platinum can be found here. Find the complete history of all platinum group metals here.

A History Of Iridium

The history of iridium encompasses scientific breakthroughs, industrial applications, and technological innovations that have shaped modern science and industry. From its discovery in the residue of platinum ores to its role in advanced materials and chemical processes, iridium’s unique properties have made it indispensable in numerous fields despite being one of Earth’s rarest elements.

Chronology

  • 1803 – British chemist Smithson Tennant discovered iridium in the acid-insoluble residues of platinum ores, naming it after the Greek word iris (rainbow) due to the various colors of its compounds; Tennant’s discovery of iridium was documented in a letter to the Royal Society on June 21, 1804; French chemists H.-V. Collet-Descotils, A.-F. Fourcroy, and N.-L. Vauquelin identified iridium at approximately the same time [1, 2, 3]
  • 1813 – British scientist John George Children became the first to melt a sample of iridium using “the greatest galvanic battery that has ever been constructed” [1]
  • 1834 – John Isaac Hawkins created the first iridium-pointed gold fountain pen nib, establishing iridium’s use in writing instruments [1]
  • 1837 – British company Johnson Matthey claimed to have been using a process for melting iridium with phosphorus [1]
  • 1842 – Robert Hare obtained high-purity iridium, finding it had a density of around 21.8 g/cm³ and noting the metal as nearly immalleable and very hard [1]
  • 1860 – Henri Sainte-Claire Deville and Jules Henri Debray achieved the first melting of iridium in appreciable quantity, requiring burning more than 300 litres of pure O₂ and H₂ gas for each kilogram of iridium [1]
  • 1880 – John Holland and William Lofland Dudley patented a process for melting iridium by adding phosphorus in the United States [1]
  • 1889 – An alloy of 90% platinum and 10% iridium was used to construct the International Prototype Meter and kilogram mass at the International Bureau of Weights and Measures near Paris; The International Prototype of the Kilogram (IPK) made of platinum-iridium was formally ratified as the kilogram by the 1st CGPM [1, 4]
  • 1933 – Otto Feussner developed the first alloy of iridium with ruthenium for use in thermocouples, allowing measurement of high temperatures in air up to 2,000°C [5]
  • 1934 – The first isotope of iridium was discovered, beginning a period that would see all known isotopes of iridium discovered between 1934 and 2008 [1]
  • 1944 – Parker began fitting the Parker 51 fountain pen with nibs tipped by a ruthenium and iridium alloy containing 3.8% iridium [1]
  • 1948 – The International Prototype Kilogram, made of 90% platinum and 10% iridium alloy, underwent its second verification showing mass changes relative to other iridium-platinum copies [4]
  • 1952 – The last fountain pen nib found to contain actual iridium (2.6%) was sampled from a Parker 51 [6]
  • 1957 – Rudolf Mössbauer discovered the Mössbauer effect using iridium-191 in Munich, Germany, leading to his Nobel Prize in Physics in 1961 [1]
  • 1960 – The International Prototype Meter bar made of 90% platinum and 10% iridium was replaced as the definition of the meter [1]
  • 1965 – Jerry J. Rubin and Le Grand G. Van Uitert filed a patent for coating iridium crucibles with zirconium to extend their lifetime in crystal growth applications [7]
  • 1980 – Luis Alvarez and team discovered an iridium-rich clay layer at the Cretaceous-Paleogene boundary, leading to the asteroid impact theory for dinosaur extinction based on high iridium concentrations [8]
  • 1989 – The International Prototype Kilogram made of platinum-iridium alloy underwent its third and final verification, showing the iridium-containing standard had mass variations compared to its copies [4]
  • 1995 – BP Chemicals commercialized the Cativa process, using iridium catalysts for methanol carbonylation to produce acetic acid [9]
  • 1996 – BP Chemicals announced the new Cativa process for acetic acid production using iridium catalysts promoted by ruthenium [10]
  • 1997 – DENSO developed iridium spark plugs with ultra-thin iridium electrodes, improving wear resistance and ignition performance [11]
  • 1998 – DENSO created IRIDIUM POWER spark plugs with 0.4 mm diameter iridium center electrodes, the world’s smallest at the time [11]
  • 1999 – Baldo et al. demonstrated that phosphorescent dyes containing iridium in OLEDs could achieve improved efficiency through triplet harvesting [12]
  • 2000 – Iridium crucibles became widely used for growing single crystals by the Czochralski method for semiconductor applications [13]
  • 2004 – Iridium complexes such as Ir(mppy)₃ became a focus of research for phosphorescent OLEDs containing iridium [14]
  • 2008 – The most recent iridium isotopes (²⁰⁰⁻²⁰²Ir) were discovered, completing identification of iridium isotopes from mass 164 to 202 [1]
  • 2011 – Bosch introduced new iridium spark plugs using proprietary iridium alloy and 360-degree laser welding processes; Demonstration of thermally activated delayed fluorescence (TADF) in OLEDs offered alternative to iridium-based phosphorescent emitters [15, 16]
  • 2013 – 88% of vehicles from 2013-2018 came with iridium spark plugs as original equipment, reversing decades of nickel plug dominance [17]
  • 2015 – Research showed iridium catalysts with pyridinylphosphinate ligands as potential blue phosphorescent materials for OLEDs containing iridium [18]
  • 2018 – Worldwide iridium production reached approximately 7,300 kilograms [1]
  • 2019 – The kilogram was redefined based on Planck’s constant, ending the role of the International Prototype Kilogram made of platinum-iridium alloy after 130 years [19]
  • 2020 – Iridium crucibles market continued growth for semiconductor manufacturing, with iridium crucibles essential for LED substrate manufacturing [20]
  • 2021 – Research on [3+2+1] coordinated iridium(III) complexes for blue phosphorescent OLEDs demonstrated quantum efficiency of 84 ± 5% using iridium [21]
  • 2022 – Worldwide demand for iridium in industrial applications including iridium crucibles for crystal growth reached new highs [22]
  • 2023 – Global iridium production estimated at 6,800 kilograms annually; iridium crucibles market was valued at USD 135.7 million, expected to reach USD 245.6 million by 2031 [1, 23]
  • 2024 – Research continued on iridium-free blue phosphorescent OLED emitters to reduce dependence on rare iridium metal [16]
  • 2025 – Iridium price forecasts indicated continued demand for iridium in electrolyser technologies for green hydrogen production [24]

Final Thoughts

The history of iridium reflects humanity’s evolving relationship with rare elements and advanced materials. From Smithson Tennant’s careful analysis of platinum residues to modern applications in catalysis and electronics, iridium has repeatedly demonstrated its unique value despite extreme scarcity. Its journey from laboratory curiosity to industrial catalyst, from fountain pen tips to high-temperature crucibles, illustrates how a single element’s exceptional properties can drive innovation across centuries.

As we face future challenges in sustainable technology, green hydrogen production, and materials science, iridium’s story reminds us that even the rarest elements can have profound impacts on human progress. The ongoing search for iridium alternatives in some applications, coupled with new uses in emerging technologies, ensures that this remarkable element will continue to shape scientific and industrial advancement for generations to come.

Thanks for reading!

References

[1] Iridium – Wikipedia – https://en.wikipedia.org/wiki/Iridium

[2] Iridium – New World Encyclopedia – https://www.newworldencyclopedia.org/entry/Iridium

[3] Iridium | Definition, Properties, & Uses | Britannica – https://www.britannica.com/science/iridium

[4] International Prototype of the Kilogram – Wikipedia – https://en.wikipedia.org/wiki/International_Prototype_of_the_Kilogram

[5] Otto Feussner – Wikipedia – https://de.wikipedia.org/wiki/Otto_Feussner

[6] How can we talk about iridium? | Nibs – https://www.nibs.com/blog/nibster-writes/how-can-we-talk-about-iridium

[7] US3470017A – Iridium crucibles and technique for extending the lifetime thereof by coating with zirconium or zirconium oxide – Google Patents – https://patents.google.com/patent/US3470017A/en

[8] Iridium anomaly – Wikipedia – https://en.wikipedia.org/wiki/Iridium_anomaly

[9] Reactivity of Ir( iii ) carbonyl complexes with water: alternative by-product formation pathways in catalytic methanol carbonylation – Dalton Transactions (RSC Publishing) – https://pubs.rsc.org/en/content/articlehtml/2013/dt/c3dt52092g

[10] The Cativa™ Process for the Manufacture of Acetic Acid | Johnson Matthey Technology Review – https://technology.matthey.com/content/journals/10.1595/003214000X44394105

[11] HISTORY OF DENSO SPARK PLUG | SPARK PLUG | Automotive Service Parts and Accessories | DENSO Global Website – https://www.denso.com/global/en/products-and-services/automotive-service-parts-and-accessories/plug/history/

[12] Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials – PMC – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2635741/

[13] Iridium Crucibles Supplier – SAM – https://www.samaterials.com/iridium/887-iridium-crucibles.html

[14] OLED – Wikipedia – https://en.wikipedia.org/wiki/OLED

[15] Bosch Introduces New Iridium Spark Plug – aftermarketNews – https://www.aftermarketnews.com/bosch-introduces-new-iridium-spark-plug/

[16] History of OLED materials and technology – https://noctiluca.eu/history-of-oled-materials-and-technology/

[17] The Evolution Of Spark Plugs – – https://www.tomorrowstechnician.com/spark-plug-evolution/

[18] Novel Design of Iridium Phosphors with Pyridinylphosphinate Ligands for High-Efficiency Blue Organic Light-emitting Diodes | Scientific Reports – https://www.nature.com/articles/srep38478

[19] Kilogram – Wikipedia – https://en.wikipedia.org/wiki/Kilogram

[20] Unveiling the Iridium Crucible in Artificial Crystal Growth – https://www.samaterials.com/content/the-container-of-artificial-crystal-growth-iridium-crucible.html

[21] Frontiers | Highly Efficient Phosphorescent Blue-Emitting [3+2+1] Coordinated Iridium (III) Complex for OLED Application – https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2021.758357/full

[22] A comprehensive quarterly iridium and ruthenium market report and iridium price outlook on SFA (Oxford)’s iridium market fundamentals and integration of future green hydrogen technologies for new and existing end-uses. – https://www.sfa-oxford.com/platinum-group-metals/pgm-market-reports/iridium-and-ruthenium-market-report/

[23] Global Iridium Crucibles Market Analysis: Size, Share & Industry Outlook 2033 – https://www.marketresearchintellect.com/product/global-iridium-crucibles-market-size-and-forecast/

[24] A comprehensive quarterly iridium and ruthenium market report and iridium price outlook on SFA (Oxford)’s iridium market fundamentals and integration of future green hydrogen technologies for new and existing end-uses. – https://www.sfa-oxford.com/platinum-group-metals/pgm-market-reports/iridium-and-ruthenium-market-report/