The Collaborative International Dictionary
fassaite
Pyrgom \Pyr"gom\, n. [Gr. ? a place furnished with towers, fr. ? a tower.] (Min.) A variety of pyroxene; -- called also fassaite.
Wiktionary
fassaite
n. (context mineral English) A variety of pyroxene.
Wikipedia
Fassaite
Fassaite is a variety of augite with a very low iron content, Ca(Mg,Fe,Al)(Si,Al)O. It is named after the Fassa Valley, Italy.
It is thought to be a contact mineral formed at high temperature on the interface between volcanic rocks and limestone. It is also reported in meteorites.