Zinnwaldite, KLiFeAl(AlSi<sub>3</sub>)O<sub>10</sub>(OH,F)<sub>2</sub>, potassium lithium iron aluminium silicate hydroxide fluoride, is a silicate mineral in the mica group. The IMA status is as a series between siderophyllite (KFe<sub>2</sub>Al(Al<sub>2</sub>Si<sub>2</sub>)O<sub>10</sub>(F,OH)<sub>2</sub>) and polylithionite (KLi<sub>2</sub>AlSi<sub>4</sub>O<sub>10</sub>(F,OH)<sub>2</sub>) and not considered a valid mineral species.
It was first described in 1845 in Zinnwald/Cinvald (today CÃÂnovec) on the German-Czech Republic border.
It occurs in greisens, pegmatite, and quartz veins often associated with tin ore deposits. It is commonly associated with topaz, cassiterite, wolframite, lepidolite, spodumene, beryl, tourmaline, and fluorite.