In the letter, the company’s lawyers say that unless Rio Tinto has a satisfactory response to the detailed allegations set out in the document, BSGR will sue Rio Tinto in the English High Court to recover its losses, which run to several billions of dollars.

The move comes in response to the recently unveiled e-mails sent by Rio’s executives in May 2011 and a related dubious payment made to external consultant Francois de Combret, which has triggered several probes as well as a management shakeup.

“These new developments are damning evidence against Rio Tinto demonstrating that Rio Tinto had a central role in bringing about BSGR’s loss of mining rights in Simandou, Guinea,” the letter says.

Before claims can be issued in England, parties are required to set out their intended positions by way of pre-action correspondence. With the document sent today, BSGR has taken this first step in what it can be a long-dragged fresh dispute over Simandou, the world’s biggest untapped iron-ore deposit.

Chequered history

Rio Tinto had the licence for the entire Simandou deposit since the early 1990s, but was stripped of the northern blocks of it in 2008.

BSGR acquired such concession later that year after spending $160 million exploring the property. But in 2010, it sold 51% of its holdings to Vale (NYSE:VALE) for $2.5 billion. The Rio de Janeiro-based company stopped paying after the first $500 million after missing a number of development milestones. Then, the new Guinean government under Alpha Conde launched a review of all mining contracts awarded under previous regimes and launched an investigation into the Vale-BSGR joint venture.

Shortly after authorities withdrew their mining permit and accused BSGR of obtaining its rights through corruption. BSGR has denied wrongdoing and filed an arbitration request in an attempt to win compensation from the Western African nation

BSGR claims Rio Tinto contributed to the loss of its mining rights in Simandou.

In 2014, Rio filed a lawsuit against Vale (NYSE:VALE) and BSG Resources over an alleged conspiracy between the two competitors to steal its rights over the project. Rio alleged BSGR paid a $200 million bribe to Guinea’s former minister using funds from Vale’s initial payment.

The US district court threw out the case in November 2015, saying Rio “had waited too long to file the lawsuit” under the Racketeer Influence and Corrupt Organizations Act, which calls for a four year time limit.

Simandou, with over two billion tonnes of reserves and some of the highest grades in the industry (66% – 68% Fe which attracts premium pricing), one of the most easily exploitable iron ore fields outside of Australia’s Pilbara region and Brazil.

At full production, the concession would export up to 100 million tonnes per year – that’s a third of Rio’s total capacity at the moment – and would catapult Rio past Vale as world number one iron ore miner. Simandou would by itself be the world’s fifth-largest producer behind Australia’s Fortescue Metals and BHP Billiton.