Siderophyllite
Siderophyllite is a rare member of the mica group of silicate minerals with formula KFe2Al(Al2Si2)O10(F,OH)2.
The mineral occurs in nepheline syenite pegmatites and granite and aplite greisens. It is associated with microcline and astrophyllite at Pikes Peak, Colorado. It is also found in the alkali pegmatites of Mont Saint-Hilaire, Quebec.