Ruthenium is a chemical element with the symbol Ru, atomic number 44 and CAS number 7440-18-8, one of the six platinum group metals. This hard, brittle, silvery-white metal melts at 2,334 °C and reached the market as 972 koz (30.2 tonnes) of primary supply in 2025, according to Johnson Matthey.
What Is Ruthenium?#
Ruthenium is not a rare earth element. Ruthenium is a platinum group metal and a transition metal in period 5, group 8, sharing period 5 with rhodium, palladium and silver and group 8 with osmium. It fills the 4d electron shell, while the lanthanides fill the 4f shell between barium and hafnium. Ruthenium shares ores and refineries with the other platinum group metals.
Ruthenium Quick Facts#
Ruthenium's atomic number is 44, its standard atomic weight is 101.07 and its CAS number is 7440-18-8. The table lists its identity data, with the atomic weight from CIAAW (IUPAC).
| Property | Value |
|---|---|
| Symbol | Ru |
| Atomic number | 44 |
| CAS number | 7440-18-8 |
| Standard atomic weight | 101.07(2) (CIAAW) |
| Period / group | 5 / 8 |
| Element type | Transition metal, platinum group metal |
| Standard state | Solid, hexagonal close-packed |
| Electron configuration | [Kr]4d⁷5s¹ |
| Discovered | 1844 |
| Discoverer | Karl Ernst Claus, Kazan University |
| Name origin | Ruthenia, Latin for Russia |
Ruthenium Among the Platinum Group Metals#
Ruthenium is one of six platinum group metals, alongside platinum, palladium, rhodium, iridium and osmium. It has the lowest atomic weight of the six and forms the light 4d triad with rhodium and palladium (12.0 to 12.4 g/cm³); osmium, iridium and platinum form the heavy 5d triad (21.5 to 22.6 g/cm³).
Ruthenium Properties#
Ruthenium has a density of 12.364 g/cm³ at 20 °C and melts at 2,334 °C (2,607 K), the highest melting point of the three light platinum group metals and third of all six, after osmium and iridium. It boils at 4,150 °C (4,423 K). The full data sheet of ruthenium properties is on the ruthenium properties page.
Physical Properties: Density, Melting Point and Hardness#
Ruthenium crystallizes in the hexagonal close-packed structure, with a c/a ratio of 1.5824, well below the ideal 1.633. This compression makes ruthenium stiff and brittle: Young's modulus 447 GPa, nearly 2.7 times platinum's, and Mohs hardness 6.5.
Ruthenium density sources disagree: modern 12.364 g/cm³, legacy Johnson Matthey 12.45 g/cm³, PubChem 12.1 g/cm³. The ruthenium density page compares them.
Ruthenium and osmium are the only hexagonal platinum group metals.
| Property | Ruthenium (Ru) | Osmium (Os) |
|---|---|---|
| Crystal structure | Hexagonal close-packed | Hexagonal close-packed |
| Lattice parameters a / c (20 °C) | 270.58 / 428.16 pm | 273.42 / 431.99 pm |
| Space group | P6₃/mmc | P6₃/mmc |
| c/a ratio | 1.5824 | 1.5800 |
| Common oxidation states | +3, +4 | +2, +3, +4, +8 |
| Full oxidation-state range | −2 to +8 | −2 to +8 |
| Electron configuration | [Kr]4d⁷5s¹ | [Xe]4f¹⁴5d⁶6s² |
Older handbooks give 2,310 °C, 24 °C below today's value; the ruthenium melting point page covers both.
Electron Configuration and Oxidation States#
Ruthenium's ground-state electron configuration is [Kr]4d⁷5s¹, and its common oxidation states are +3 and +4, within a full observed range of −2 to +8. Ruthenium and osmium are the only platinum group metals reaching +8, in RuO4 and OsO4. PubChem lists only +3 as common, an oversimplification. See ruthenium electron configuration for the orbital filling.
Is Ruthenium Magnetic?#
Ruthenium is paramagnetic, with a molar magnetic susceptibility of +39 × 10⁻⁶ cm³/mol at 298 K, so a magnet attracts it only weakly; no pure platinum group metal is ferromagnetic. Palladium (+567.4), platinum (+201.9) and rhodium (+111.0) respond more strongly, iridium and osmium less. Below 0.51 K, ruthenium becomes a superconductor.
Where Ruthenium Comes From#
Nearly all ruthenium comes from the UG2 Chromitite layer of South Africa's Bushveld Complex, as a co-product of platinum and palladium mining; no mine produces ruthenium alone. The main ruthenium mineral, laurite (RuS2, Mohs hardness 7.5), is closely associated with chromite, which is why chromite-rich UG2 ore is ruthenium-rich. The ruthenium occurrence page covers the minerals.
Ruthenium Occurrence and Ores#
Implats-derived prill splits put UG2 ruthenium at 9.9 to 15.9% of 6E metal content (platinum, palladium, rhodium, ruthenium, iridium and gold) across Implats' own operations, against 5.4 to 7.9% in Merensky Reef ore. The table derives each share from Implats' Mineral Resource and Mineral Reserve Statement 2025 (as at 30 June 2025).
| Operation | UG2 ruthenium, % of 6E | Merensky ruthenium, % of 6E |
|---|---|---|
| Impala Rustenburg | 9.9 | 6.8 |
| Impala Bafokeng | 15.3 | 7.9 |
| Afplats (Leeuwkop) | 15.9 | Not reported |
| Marula | 11.4 | 5.4 |
| Two Rivers | 13.3 | 6.8 |
| Zimplats and Mimosa (Great Dyke MSZ, Zimbabwe) | 3.4 to 3.9 (MSZ) | Not applicable |
World Ruthenium Production#
World platinum mine production was about 170,000 kg (170 tonnes) in 2025 (USGS Mineral Commodity Summaries 2026, February 2026); world primary ruthenium supply was far smaller, 972 koz (30.2 tonnes) in 2025 on Johnson Matthey's May 2026 figures. Demand of 1,265 koz left "a shortfall of almost a quarter of annual consumption." Each figure keeps its own publisher and basis.
| Measure (2025) | Value | Source |
|---|---|---|
| World platinum mine production | ~170,000 kg (170 t) | USGS MCS 2026, February 2026 (estimate) |
| World primary ruthenium supply | 972 koz (30.2 t) | Johnson Matthey PGM Market Report, May 2026 |
| World ruthenium demand | 1,265 koz (39.3 t) | Johnson Matthey PGM Market Report, May 2026 |
| Ruthenium market balance | −293 koz | Johnson Matthey PGM Market Report, May 2026 |
| South Africa share of primary ruthenium | Over 85% | Johnson Matthey PGM Market Report, May 2026 |
Ruthenium Discovery and History#
Ruthenium had two withdrawn discovery claims before its confirmed discovery: Jędrzej Śniadecki in 1807-1808 and Gottfried Osann in 1827-1828, both unable to confirm their findings. Śniadecki called his metal "vestium"; Osann, working on Ural residues with Jöns Jakob Berzelius, claimed three metals, among them "ruthenium".
Karl Ernst Claus isolated ruthenium in 1844 at Kazan University, recovering 6 grams from Ural platinum-ore residues, and reused Osann's name after Ruthenia, Latin for Russia. G. I. Hess presented Claus's letter to the St Petersburg Academy of Sciences on 13 September 1844, Berzelius verified the samples, and Claus won the 5,000-ruble Demidov Prize. Ruthenium is the last platinum group metal discovered and the only one named after a country. The ruthenium discovery page covers the dispute.
Ruthenium Uses#
Ruthenium's main uses are chemical catalysts, electrical components such as chip resistors and hard-disk layers, and chlor-alkali electrodes. The IPA and SFA (Oxford) Ruthenium Factsheet 2026 splits 2025 demand into four blocks.
- Chemical: 45% (about 18 tonnes), notably caprolactam and adipic acid catalysts
- Electrical: 32% (about 13 tonnes), mainly chip resistors, hard-disk media and contacts
- Other: 13% (about 5 tonnes), including jewelry alloys and anti-glare mirror coatings
- Electrochemical: 10% (about 4 tonnes), mainly chlor-alkali anode coatings
See ruthenium uses for each application.
Electrical Contacts and Chip Resistors#
Thick-film chip resistors and electrical contacts belong to ruthenium's electrical block, 32% of 2025 demand (IPA/SFA, 2026), which puts ruthenium oxide paste in resistors "for almost every chip device." Ruthenium also hardens platinum and palladium contact alloys, and RuO2-based anodes have served chlor-alkali electrolysis since the 1960s.
Catalysis: Metathesis and Transfer Hydrogenation#
Ruthenium underlies two Nobel Prizes in Chemistry: Robert Grubbs' 1992 ruthenium metathesis catalyst (shared 2005 prize with Yves Chauvin and Richard Schrock) and Ryoji Noyori's ruthenium transfer-hydrogenation catalysts (2001 prize). Industrial catalysis is larger in tonnage: Johnson Matthey (May 2026) reports Chinese chemical-industry PGM purchasing of nearly 1 million oz in 2025, driven above all by ruthenium caprolactam and adipic acid catalysts.
Other Industrial Uses#
Ruthenium has been used in hard-disk drive perpendicular-recording layers since the 1990s. Heraeus (Precious Appraisal, 11 August 2025) ties the recent demand rebound to AI data storage, while newer HAMR media use much less ruthenium per drive. Ruthenium also leads the candidates to replace copper in chip interconnects at 2 nm and beyond (imec, 30 nm metal pitch, October 2020). Smaller uses include ammonia cracking and Pt950/Ru jewelry alloy.
Ruthenium Compounds#
Ruthenium's commercial chemistry starts from ruthenium(III) chloride hydrate (CAS 14898-67-0), the universal precursor for Grubbs catalysts, [Ru(bpy)3]2+ and RuO2 electrode inks; the anhydrous salt (CAS 10049-08-8) is insoluble. Its hydration varies, so suppliers sell it on a stated ruthenium assay. The table lists four core compounds; ruthenium compounds covers the family.
| Compound | Formula | CAS | Solubility in water | Primary use |
|---|---|---|---|---|
| Ruthenium(III) chloride, anhydrous | RuCl3 | 10049-08-8 | Insoluble | Laboratory material; not the traded form |
| Ruthenium(III) chloride hydrate | RuCl3·xH2O | 14898-67-0 | Soluble | Precursor for Grubbs catalysts, [Ru(bpy)3]2+, RuO2 inks, plating |
| Ruthenium tetroxide | RuO4 | 20427-56-9 | 2% w/v at 20 °C | Ruthenium refining by volatilization; strong oxidant |
| Ruthenium(IV) oxide | RuO2 | 12036-10-1 | Insoluble | Chlor-alkali anode coatings, thick-film resistors |
Is Ruthenium Toxic?#
Ruthenium metal is not classified as a health hazard, but ruthenium tetroxide (RuO4) is a strong oxidizer (GHS H271) that also causes serious eye irritation (H319). The IPA/SFA Ruthenium Factsheet 2026 calls RuO4 "much more toxic" but notes it "exists in only very small quantities."
Solid ruthenium tetroxide melts at 25.5 °C and is explosively unstable above roughly 100 °C; all 104 ECHA C&L Inventory reports (via PubChem) classify it H271 and H319. Ruthenium has no entry in OSHA Table Z-1 (checked 6 August 2026).
Soluble salts differ: 95.1% of ECHA notifications classify ruthenium(III) chloride as skin-corrosive (H314). See ruthenium toxicity.
Ruthenium Isotopes#
Ruthenium has seven naturally occurring isotopes, as many as osmium and more than any other platinum group metal, with ruthenium-102 the most abundant at 31.6%.
| Isotope | ⁹⁶Ru | ⁹⁸Ru | ⁹⁹Ru | ¹⁰⁰Ru | ¹⁰¹Ru | ¹⁰²Ru | ¹⁰⁴Ru |
|---|---|---|---|---|---|---|---|
| Natural abundance | 5.54% | 1.87% | 12.8% | 12.6% | 17.1% | 31.6% | 18.6% |
Synthetic ruthenium-106 (half-life 371.8 days) is a uranium and plutonium fission product, monitored after reactor accidents because RuO4 is volatile. The ruthenium isotopes page lists the radioisotopes.
Ruthenium Price, Investing and Scrap#
Ruthenium's price, investment options and scrap value each have a dedicated page; no exchange contract, futures, fixing or ETF exists for ruthenium. Supply and demand sit on the ruthenium market page.
Ruthenium Price Today#
DailyPlatinum publishes a live ruthenium price page in troy ounces, grams and kilograms, with source and timestamp. Past quotes sit on the ruthenium price chart.
Investing in Ruthenium#
Ruthenium investment is limited to powder, sponge and specialist dealers, unlike platinum's bars, coins and ETFs. Heraeus sells ruthenium "in the form of sponge or powder" at a minimum 99.9% purity (see ruthenium sponge).
Johnson Matthey quotes per troy ounce and Umicore per gram; a troy ounce converter bridges the two, and ruthenium investment covers buying.
Selling Ruthenium Scrap#
Ruthenium scrap is recovered almost entirely through closed-loop industrial recycling: 42 tonnes in 2024, 100% closed loop, per Johnson Matthey's Circularity Whitepaper 2024 as cited by the IPA/SFA factsheet. Open-loop recovery is undeveloped because end products hold very little ruthenium. Refiners buying scrap platinum group metals pay on assayed content.
Ruthenium vs the Other Platinum Group Metals#
Ruthenium sits next to rhodium in the periodic table and close to it in density, 12.364 against 12.423 g/cm³, though it melts 370 °C higher.
| Metal | Density at 20 °C (g/cm³) | Melting point (°C) | Common oxidation states |
|---|---|---|---|
| Ruthenium (Ru) | 12.364 | 2,334 | +3, +4 |
| Rhodium (Rh) | 12.423 | 1,964 | +3 |
| Palladium (Pd) | 12.007 | 1,554.9 | 0, +2, +4 |
| Osmium (Os) | 22.587 | 3,033 (handbook value) | +2, +3, +4, +8 |
| Iridium (Ir) | 22.562 | 2,446 | +3, +4 |
| Platinum (Pt) | 21.452 | 1,768.3 | +2, +4 |
Ruthenium FAQ#
Is ruthenium a rare earth element? No. Ruthenium is a platinum group metal, a transition metal in period 5, group 8.
What is ruthenium used for? Chemical catalysts (45% of 2025 demand), electrical components such as chip resistors (32%), other uses including jewelry alloys (13%) and chlor-alkali electrodes (10%), per IPA/SFA 2026.
Is ruthenium worth anything? Yes. Johnson Matthey, Heraeus and Umicore quote it daily; the current value per ounce is on the ruthenium price today page.
Does ruthenium react with air? At high temperature, yes: in air it forms volatile oxides instead of a protective scale (Jehn, 1984). Ruthenium resists acids, including aqua regia, and dissolves only in fused alkalis.
Is ruthenium magnetic? Only weakly: it is paramagnetic, never ferromagnetic.
What is dark ruthenium? A dark ruthenium-plated finish; ruthenium plating starts from ruthenium(III) chloride hydrate, and no standard composition for the finish is established. Ruthenium black is a separate product.
How many isotopes does ruthenium have? Seven naturally occurring, ruthenium-96 to ruthenium-104; ruthenium-102 is the most abundant at 31.6%.