SYDNEY, AAP – Rio Tinto misled investors when it failed to reveal some coal operations were no longer economically viable, a court has found.

The Federal Court ruled the mining giant failed share market obligations by not passing on information that Rio Tinto Coal Mozambique could not continue as a top coking coal resource.

The miner later revealed a charge of $US14 billion in its 2012 full-year earnings, which included $US3 billion from the Mozambique coal.

Rio Tinto must pay a $750,000 fine and the costs of proceedings.

Then-leaders Tom Albanese and Guy Elliot, who were chief executive and chief financial officer at the time, had claims against them dismissed.

The Australian Securities and Investments Commission, which filed the charges, agreed to the outcomes with Rio Tinto.

The miner said there were no findings of fraud or systemic failure.

A UK regulator made similar claims over the Mozambique coal operations. The two groups settled in 2017.

The US Securities and Exchange Commission is also pursuing the miner over the same failings.

Rio Tinto said it will defend the claims.

Companies trading on the share market must tell investors information in a timely manner that could affect the value of their shares.

Rio Tinto sold its Mozambique coal arm in 2014.

Shares in the miner on the ASX were down 0.19 per cent to $126.32 at 1521 AEDT.