the word 'taconite' is a direct borrowing from the name of the taconic mountains, a range in the northeastern united states. geologists first identified this specific, hard, siliceous iron formation in this region in the 19th century. consequently, the rock was named after its geographical origin, following a common practice in mineralogy and geology. over time, the term became standardized in mining and industrial contexts to refer to this particular type of low-grade iron ore, regardless of where it is found.

this is a toponymic simplex word, derived directly from a place name. it does not contain separable, productive morphemes in english.