Osmium

Overview

Osmium is a bluish-white, extremely hard and brittle platinum-group metal (PGM). Smithson Tennant isolated it in 1803 from the residue left after dissolving platinum in aqua regia.¹ It is the densest naturally occurring element and has a very high melting point of 3,033 °C.²

The metal itself is not toxic, but it readily forms osmium tetroxide (OsO₄), a volatile and highly toxic oxide that can damage the lungs, skin and eyes.¹ That compound is also the basis of osmium's main uses, as a catalyst in chemical synthesis and a stain for electron microscopy.²

Osmium differs from the other PGMs in its list status. It is not on the final 2025 US List of Critical Minerals, which names platinum, palladium, iridium, rhodium and ruthenium individually but not osmium.³ In the EU it is covered only through the group entry "Platinum Group Metals", which appears on both the critical and the strategic raw materials lists.⁴

Where it comes from

Osmium is never mined for its own sake. It occurs in trace amounts in PGM ores and is obtained, if at all, as a by-product of platinum and nickel refining.² Most PGM resources are in South Africa's Bushveld Complex, Zimbabwe's Great Dyke and Russia's Norilsk-Talnakh intrusions, and the UG2 chromitite reef in the Bushveld carries relatively high proportions of the minor PGMs, including osmium.²

Whether osmium is recovered depends on refinery flowsheets. It follows ruthenium through the refining circuit and is driven off as OsO₄ during ruthenium purification, often into vent scrubbers rather than a saleable product. In South African circuits most osmium is treated as an impurity and lost before final refining, and two of the four major South African refineries do not recover it at all.² Russian osmium recovery and sales had stopped entirely by the end of the 2010s.²

As a result, South Africa is the dominant source of osmium-bearing refinery streams, and recovery is concentrated in a small number of specialist refiners in South Africa, Germany, the UK and the United States.² Companies do not report osmium production. Based on ore grades and company and expert guidance, consultancy SFA (Oxford) estimates world output at about 500–550 kg a year in 2024 and 2025.² Because no official country-by-country data exist, no production chart is shown here.

Osmium reserves are not reported separately. Applying an assumed osmium share of 0.1–0.5% to global PGM reserves, the same study estimates contained osmium at roughly 76–380 t, with a best estimate of about 150 t.²

What it is used for

The chemical sector is the main market. Osmium tetroxide and osmate salts are used as oxidants and catalysts for dihydroxylation reactions in stereoselective organic synthesis, making high-value fine chemicals, pharmaceutical intermediates and agrochemicals.²

Osmium compounds are also used to stain and fix tissue samples for electron microscopy, where they preserve cell membranes and enhance contrast. This use consumes the osmium.²

Metallic uses are niche. Osmium forms extremely hard alloys for fountain pen tips, instrument pivots, needles and electrical contacts.¹ A platinum alloy with 10% osmium is used in surgical implants, including pacemaker components and replacement pulmonary valves.² Research on osmium-based anticancer compounds and electrocatalysts remains at an academic or exploratory stage.²

Grades and forms

Osmium is sold as metal sponge and as compounds, including osmium tetroxide and osmate salts, in solid, powder and solution forms.² There is no exchange-traded benchmark, and products are priced transaction by transaction.²

Trade and policy

Osmium trade is hard to track because customs classifications group it with iridium and ruthenium.² The United States reported osmium imports of about 57 kg in 2025, compared with 1 kg or less in each of the previous four years.⁵ European suppliers of osmium compounds depend mainly on imports from South Africa, so supply disruptions affecting other PGM streams also affect osmium.²

Osmium tetroxide is classified as acutely toxic by swallowing, inhalation and skin contact. For transport it is UN 2471, Class 6.1, Packing Group I, which requires specific labeling and handling controls.²

Recycling and substitution

Open-loop recycling of osmium is very limited. The quantities in products are tiny, processing is complex and hazardous, and the metal's value is rarely high enough to justify recovery. Some closed-loop recycling may occur in chemical processes, but osmium is often lost in use or discarded as waste.²

For OsO₄-catalyzed reactions, alternative catalysts exist but usually give poorer selectivity, which adds costly purification steps. Chemical producers tend to stay with proven routes rather than requalify their processes unless supply problems force a change.²

Sources

1. Osmium: element information, properties and uses. Royal Society of Chemistry, accessed 2026-10-03. ↩ ↩² ↩³

2. PGM Fact Sheet: Osmium (May 2026). International Platinum Group Metals Association, accessed 2026-10-03. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰

3. Final 2025 List of Critical Minerals (90 FR, 7 November 2025). Federal Register, accessed 2026-10-03. ↩

4. EU critical raw materials. European Commission Joint Research Centre (RMIS), accessed 2026-10-03. ↩

5. Mineral Commodity Summaries 2026: Platinum-Group Metals. U.S. Geological Survey, accessed 2026-10-03. ↩