Kimberlite residues mineralize CO 2 from the air into magnesium carbonate minerals [1]. These carbonation rates can be accelerated by increasing the supply of CO 2 into the tailings through injection of concentrated sources, such as diesel flue gas from mine power generation [2]. Successful injection requires careful management of physical properties (moisture content, particle size distribution, degree of compaction, and permeability) to optimize the chemical reactions and make largescale implementation feasible. These factors and their relationship to successful CO 2 injection were assessed through Proctor compaction and permeability testing and the findings were used to inform an experimental design. This experiment injected simulated flue gas into a 550 kg square meter pad of processed kimberlite from the Gahcho Kué Diamond Mine (NT, Canada), which represented a section of a larger mine-scale design. Injected CO 2 was removed from the gas phase into carbonate minerals in the solid phase as confirmed by increases in total inorganic carbon. The magnitude of carbon captured (1.4 kt CO 2 per Mt processed kimberlite) approached that attained from an idealized centimetre-scale injection experiment on the same material (2.1 kt CO 2 per Mt). This degree of reactivity implies Gahcho Kué could sequester 10 -15% of their power generation emissions in their mine waste, and the success of the experimental design proposes a manner to do so.[1] Subarctic weathering of mineral wastes provides a sink for atmospheric CO 2 , Wilson et al. (2011), Environmental Science and Technology 45, 7727-7736.[2] Strategies for enhancing carbon sequestration in Mg-rich mine tailings, Harrison et al. (2013b), Proceedings of International Mine Water Association, 593-598.

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