Rio Tinto and BHP: The Operators It Depends OnNarrow moat

Mitsui & Co. (8031) — moat facet

Rio Tinto and BHP run the mines that produce a third of Mitsui's profit, and keep inviting it into new ones.

Mitsui's largest business is run by others. Rio Tinto operates Robe River with 53% against Mitsui's 33% and Nippon Steel's 14%1; BHP operates the Mount Newman joint venture and holds 85% of Ministers North2. The Australian iron ore business contributed ¥218.7 billion to Mitsui in the latest year3.

Operator share of Mitsui iron ore ventures (%)53%Rio Tinto at Robe River85%BHP at Ministers North33%Mitsui at Robe River7%Mitsui at Ministers NorthMitsui releases, October 2025 and July 2026
Partners that own more and run everything.

These relationships are neither rivalry nor supply in the usual sense. The operators sell iron ore on their own account into the same markets, so they compete with the ventures they run for nothing; they share them. What Mitsui depends on is their operating skill, their capital discipline and their willingness to keep inviting it into new projects.

The history suggests the relationship works. Mitsui has been in Robe River since 1965 and in Mount Newman offtake since 19664, and it joined Rhodes Ridge in 2025 with Rio Tinto as operator5.

The measure is new project invitations. Participation in each new Pilbara development would confirm the partnership; being left out of one would show its limits.

Moat trajectory: Widening

Rhodes Ridge with Rio Tinto and Ministers North with BHP extended both relationships.

The number that tests this moat
Reported
Australian iron ore contribution, latest year
¥218.7bn

The profit from mines run by partners; watch it against the operators' own results.

Source: Mitsui & Co. Integrated Report 2026, data ↗
References
  1. ReportedRio Tinto operates Robe River with 53% against Mitsui's 33% and Nippon Steel's 14%; BHP operates the Mount Newman joint venture and holds 85% of Ministers North.
    Mitsui & Co. release, 7 October 2025 - sustaining investment at Robe River's West Angelas, with the interests of Rio Tinto, Mitsui and Nippon Steel. — October 2025 · publ. 7 October 2025 · source ↗
  2. ReportedRio Tinto operates Robe River with 53% against Mitsui's 33% and Nippon Steel's 14%; BHP operates the Mount Newman joint venture and holds 85% of Ministers North.
    Mitsui & Co. release, 16 July 2026 - final investment decision on Ministers North with BHP and ITOCHU. — July 2026 · publ. 16 July 2026 · source ↗
  3. ReportedThe Australian iron ore business contributed ¥218.7 billion to Mitsui in the latest year.
    Mitsui & Co. Integrated Report 2026, data section - results by operating segment: gross profit, equity-method profit, dividend income, core operating cash flow and total assets. — FY to March 2022-2026 · publ. 2026 · source ↗
  4. ReportedMitsui has been in Robe River since 1965 and in Mount Newman offtake since 1966, and it joined Rhodes Ridge in 2025 with Rio Tinto as operator.
    Mitsui & Co., Annual Securities Report for the year to March 2026 (English) - company history, employees, share price history, total shareholder return, equity production, the revenue of the Singapore trading subsidiary, competition and the Arctic LNG 2 guarantees. — FY to March 2026 · publ. 12 August 2026 · source ↗
  5. ReportedMitsui has been in Robe River since 1965 and in Mount Newman offtake since 1966, and it joined Rhodes Ridge in 2025 with Rio Tinto as operator.
    Mitsui & Co. release, 19 February 2025 - acquisition of a 40% interest in the Rhodes Ridge iron ore project for $5,342 million. — February 2025 · publ. 19 February 2025 · source ↗
Sources
Generated September 24, 2026