Ore Train to Lake Ship - Trains Magazine

MidlandMike

Iron ore is ground finer than talcum powder in ball mills, than introduced into flotation tanks where soap-like polar solution is bubbled up, which captures the metal and floats over the tank side.  The concentrate is mixed with clay and lime binder in a 2000 degree kiln to form the taconite pellets.  

What you are describing is what the mines in Eastern Quebec use to separate the Specular Hematite from the waste rock using Humphrey Spirals, where the finely ground ore travels down tall verticle spiral columns of troughs with the water and light particles sloshing over the side while the heavier Iron stays in the trough all the way to the bottom.

The mines in Minnesota and Michigan use powerful electro-magnets to pull the Magnetite

from the waste rock. The Specular Hematite (specularite) and other forms of Hematite are not strongly attracted to magnets, as such the Hematite in the Taconite ore goes out with the waste rock. The percentage of Magnetite in Taconite is high enough that the economics work out even though some iron goes out with the tailings.