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The Collaborative International Dictionary
Fahlunite

Fahlunite \Fah"lun*ite\ (f[aum]"l[u^]n*[imac]t), n. [From Fahlun, a place in Sweden.] (Min.) A hydrated silica of alumina, resulting from the alteration of iolite.

Wiktionary
fahlunite

n. (context mineral English) A hydration of iolite.