Taconite

Taconite is a variety of iron formation, an iron-bearing (> 15% iron) sedimentary rock, in which the iron minerals are interlayered with quartz, chert, or carbonate. Newton Horace Winchell, the Minnesota State Geologist, coined the term during his pioneering investigations of the Precambrian Biwabik Iron Formation of northeastern Minnesota. He noted the rock had a superficial resemblance to iron-bearing rocks from the Taconic Mountains of New York.