Deep-sea mining tests resume as lost robot rescued Patania II had been operating at a depth of 4.5 kilometers (2.8 miles) in the Clarion-Clipperton Zone — an expanse of ocean between Hawaii and Mexico that’s as big as the continental US. ( Belgium’s Global Sea Mineral Resources (GSR) has resumed tests that could lead to the mining of battery minerals from the Pacific Ocean floor after it managed to recover a robot stranded at a depth of thousands of metres. The company reported on April 28 that its Patania II, a 25-tonne mining robot prototype, had uncoupled from a 5 km long (3.1 miles) cable connecting it to the surface.