The Nicaragua-focused miner has not generated any revenue in the past two years, but narrowed pre-tax loss to £3 million in 2017 from £7.7 million a year earlier.
Soaring cobalt and lithium prices are pushing some companies to dig for them in the recycle bin, which some believe could be even more profitable than mining them.
Rio Tinto expects the global iron ore market to stay balanced through 2019 despite a likely moderation in steel demand growth in China, the world’s biggest steel consumer.