The Evolution of Flotation Performance Knowledge of Twin Metals Maturi Deposit

The Maturi project, located in the Duluth Complex of Minnesota and owned by Twin Metals Minnesota (TMM), a subsidiary of Antofagasta Minerals, is one of the world’s largest undeveloped Cu-Ni deposits containing approximately 9.0 Mt of copper and 3.0 Mt of nickel. Blue Coast Research conducted a number of metallurgical testwork programs on the deposit over the course of a decade (2012–2022) as the project was developed through scoping and pre-feasibility milestones. An optimized flowsheet of sequential flotation to produce copper and nickel concentrates was developed through this work. A comprehensive geometallurgical program was initiated in 2020 followed by a locked-cycle and mineral balancing program on carefully designed metallurgical domain composites. This work further enhanced the understanding of the metallurgical behaviour of the various value minerals in the flotation process on a spatial basis. By the time development work on the project was suspended in 2022, the metallurgical knowledge of the deposit was highly evolved. This paper presents the evolution of metallurgical knowledge on the project from the early generalized performance of large representative composites to more granular spatial domain knowledge and understanding of individual mineral behaviour and flotation performance drivers gained from the geometallurgical process coupled with mineralogical balancing.