Prices for cobalt metal, used in production of electric vehicle batteries, have tripled to nine-year peaks above $30 a pound from below $10 a pound in late 2015.
Lacklustre performances by small mining companies on the London Stock Exchange are driving rivals in need of cash to find alternative ways to raise capital.
The filing cited Anton Colbert of Cook County, Illinois, as lead plaintiff but his action acts in the name of “hundreds or thousands of members in the proposed class.”