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.