DeepGreen Metals intends to be the world’s first zero tailings miner by retrieving polymetallic base metal nodules from the seafloor. In lab tests the nuggets have been treated with calcination and smelting techniques that produced iron-rich alloy nuggets with payable amounts of nickel, copper and cobalt.
A manganese silicate product was also produced.
DeepGreen and its subsidiary NORI (Nauru Ocean Resources Inc.) are interested in the Clarion Clipperton (CC) zone in the eastern Pacific Ocean. NORI holds a 15-year exploration contract for the 74,830 km2 project area.
The company is doing further tests and engineering studies with plans of building a pilot plant next year. It will produce nickel and cobalt sulphates and copper cathode products. Suitable sites for a commercial plant are under consideration.
The nodules are typically 1 to 20 cm in diameter, 4,000 to 5,000 metres below the surface. They lie below a layer of mud up to 30 cm deep. The nodules occur as concentric layers of manganese and iron oxides and hydroxide concentrated around a core, according to DeepGreen.
Earlier this year a preliminary economic assessment put NORI inferred resources at 909 million tonnes (wet nodules) grading 1.3% nickel, 29.2% manganese, 1.1% copper and 0.2% cobalt with a mean nodule abundance of 13 kg/m2 based on a cut-off of 4 kg/m2.
Editor’s note: The company boasts of being “the world’s first zero tailings mining project.” While the claim is supported because no solid tails will be produced and stored at the mine, mining the seafloor is not without risks. The nuggets occur in mud, and the act of mining will undoubtedly create extensive turbidity of the seawater during mining. And there is considerable ecological opposition to disturbing the seafloor.
(This article first appeared in the Canadian Mining Journal)
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