taconite, a low-grade siliceous iron ore composed of 20–30 percent magnetite that occurs in fine-grained banded iron formations. Taconite is mined primarily in the U.S., in the Mesabi Iron Range in Minnesota and the Marquette Iron Range in Michigan. Recovery of the iron requires fine grinding and concentration of iron-bearing phases, which in turn are formed into pellets suitable for blast furnaces. As high-grade deposits of iron ore have become depleted, taconite deposits have increased in importance as a source of iron ore.