A highly abrasive iron ore.

a variety of chert containing magnetite and hematite; mined as a low-grade iron ore

Natural mineral containing less than 30% iron. It is the primary ore used in blast furnaces. Domestic supplies of iron-rich ores (greater than 50% iron) were largely depleted in the 1940s, so integrated steel companies now process the lower-grade taconite to make it useful.

a variety of chert which contains iron, occurring especially in the Mesabi Range of northeastern Minnesota. [AHDOS

Taconite is an iron-bearing, high-silica, flint-like rock. It is a Precambrian sedimentary rock referred to as a banded iron formation due to the typical alternating iron-rich layers and shale or chert layers. The very finely dispersed iron content, present as magnetite, is generally 25 to 30%.