UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

March 2, 2016

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:    x  Form 20-F     ¨  Form 40-F

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ¨

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934:    ¨  Yes    x  No

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): n/a

NEWS RELEASE

SAMARCO – AGREEMENT REACHED WITH BRAZILIAN AUTHORITIES

Samarco Mineracao S.A (Samarco) and its two shareholders, Vale S.A (Vale) and BHP Billiton Brasil LTDA (BHPB Brasil), have entered into an agreement with the Federal Attorney General of Brazil, the States of Espirito Santo and Minas Gerais and certain other public authorities (Brazilian Authorities) for the restoration of the environment and communities affected by the Samarco dam failure on 5 November 2015.

The Agreement provides a long-term remedial and compensation framework for responding to the impact of the Samarco tragedy.

Samarco, Vale and BHP Billiton Brasil will establish a Foundation that will develop and execute environmental and socio-economic programs to remediate and provide compensation for damage caused by the Samarco dam failure.

There are two broad types of programs included in the Agreement:

The Foundation will be governed by a seven member Board, with Samarco, BHP Billiton Brasil, and Vale each appointing two members and the Brazilian Authorities appointing one member. The Foundation will be assisted in its work by an advisory panel that will include technical experts, regulators and community representatives.

The Foundation will submit remediation and compensation programs for approval to a Council consisting of representatives of the Brazilian Authorities. The Foundation’s activities will be subject to independent external audit.

The term of the Agreement is 15 years, renewable for periods of one year successively until all obligations under the Agreement have been performed.

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Samarco will fund the Foundation with contributions as follows (calendar years):

The amount of annual contributions for each of the years 2019, 2020 and 2021 will vary between a minimum of BRL800 million (approximately US$200 million) and a maximum of BRL1.6 billion (approximately US$400 million), depending on the remediation and compensation projects which are to be undertaken in the particular year.

To the extent Samarco does not meet its funding obligations, each of Vale and BHP Billiton Brasil is liable in proportion to its 50 per cent shareholding in Samarco.

Samarco will continue to conduct and fund the humanitarian and environmental recovery and remediation work until the Foundation is operational, which is likely to be in the next few months.

The Agreement is subject to Court approval. If approved, the Agreement will settle the civil public claim commenced on 30 November 2015 by the Brazilian Authorities against Samarco, Vale and BHP Billiton Brasil which sought the establishment of a fund of up to BRL20 billion in aggregate for clean-up costs and damages relating to the dam failure.

BHP Billiton Chief Executive Officer, Andrew Mackenzie said: “This Agreement is an important step forward in supporting the long-term recovery of the communities and environment affected by the Samarco dam failure. It provides a platform for the parties to work together to support the remediation of affected areas.

“This agreement demonstrates our commitment to repairing the damage caused and to contributing to a lasting improvement in the Rio Doce.”

Further information on BHP Billiton can be found at: bhpbilliton.com

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Members of the BHP Billiton Group which is

headquartered in Australia

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This release was made outside the hours of operation of the ASX market announcements office

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.