https://www.canadianminingjournal.com/
In 1854, the land surveyor A.P. Salter noticed the needle on his compass wiggle in strange way, a signal that the bedrock on which he stood contained a huge deposit of nickel (one of the few ferromagnetic minerals that affects the orientation of old-school magnetic compasses).
Owing to its remoteness, Salter’s discovery was ignored at the time and soon forgotten. The construction of the Canadian Pacific Railway through the Sudbury basin in the early 1880s brought an influx of newcomers and a transportation link to the region.