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.