Big names like BHP and Glencore can't seem to agree on which metals will deliver the best long-term exposure to the developing global market.

Electric-car makers, battery makers, and consumer-technology companies have remained silent from the debate over deep-sea mining.

Crews are already on the site conducting mapping, sampling and prospecting work.

The Silangan project, originally slated to begin production by 2018, was hit by a ban on new open-pit mining introduced in 2017.

The firm has also completed a definitive feasibility study for its Serrote copper-gold project in Brazil.

The ruling from the U.S. District Court for Arizona challenged the U.S. Forest Service's June 2017 decision that enabled the company to move forward with a mine plan.

The approval allows for 30,000 metres of underground exploration drilling.