The blast occurred at the Reid Brook portal rock face of the expansion and was ahead of schedule.
Cobalt 27 closed on its acquisition of a cobalt stream at the Vale property on June 28; the US$300 million stream extends to the mine's expansion area.
"The blast … is the first of thousands that will take place over the life of the project and is a key milestone marking the commencement of underground construction of the Voisey's Bay mine expansion, which is expected to be an important source of cobalt outside of the DRC [Democratic Republic of Congo]," chairman and CEO Anthony Milewski said.
"Construction activities on the Voisey's Bay underground mine are now focused on starting the underground development on all four declines, with significant initial construction planned through to the end of 2018 into early 2019."
Cobalt 27's 32.6% cobalt stream is expected to return about 1.9 million pounds per year; the plan is for it to be settled in physical delivery for the life of the Voisey's Bay mine commencing in January 2021.
Vale, which confirmed in June that it would progress with the US$1.7 billion expansion project, is targeting 2021 as its first full year of production, with full-scale production by 2025. It is expected to extend Voisey's Bay's lifespan to 2034.