The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]