Yes the Mineral Range was built as narrow gauge. It was standard gauged around the time of the Duluth South Shore & Atlantic purchase of the line in 1899. The Mineral Range also owned another narrow gauge subsidiary, the Hancock & Calumet. This route was standard gauged a few years after the Mineral range was iirc. Quincy had some dual gauge tracks running at the mine and also owned 2 standard gauge steel sided mineral cars to haul concentrates from the stamp mill to the smelter via the Mineral Range ex Hancock & Calumet route.


Of note there were many narrow gauge railroads in the Keweenaw. Calumet & Hecla, Lac La Belle & Calumet, Phoenix Mine & Gratiot River, Arnold & Eagle Harbor, Mohawk Gay & Traverse Bay, plus a long list of other small mining and logging railroads across the area.