The price drop overshadowed the miner’s coal sales increase during the quarter, which totalled 6.8 million tonnes, compared with 6.3 million tonnes a year earlier.
State-owned and private companies from the UK, Germany, India, Brazil, Singapore and Russia are among those to benefit from the seabed regulator’s decision.
The shipments, the first of their kind in six months, were allowed after Sebuku Iron Lateritic Ores (SILO) and Lumbung Mineral Sentosa agreed to pay the new 20% tax.
Las Bambas will be one of the world’s largest copper mines after it starts up in 2015, with annual output equivalent to more than twice the amount of copper MMG currently produces.