FMF - Friends of Minerals Forum, discussion and message board

[Cesar M. Salvan]

The La Fossa crater, in Sicily (Italy) is a famous and beautiful magmatic system in which a complex paragenesis of very rare minerals could be found constantly in formation on its fumaroles. La Fossa is the type locality of a lot of relatively volatile mineral species with exotic compositions, more usual to the laboratory chemist than the field mineralogist (such as the ammonium tetrafluoroborate Barberiite or the metaboric acid).

Thanks to Michel Croisez, a friend from Belgium, I know the Salammoniac from La Fossa crater. In line with the exotic chemistry of the La Fossa fumaroles, the Salammoniac is also peculiar: constitutes a bromine-rich variety (NH4(Cl,Br)). In first instance, I thought about a new species, but a complete set of analysis showed a typical molar ratio Br:Cl of 1:12, with a mean of 10.1% of bromine.

As far as I know, La Fossa is the only occurrence of bromine rich Salammoniac and I found interesting to share it.