A mineral with monoclinic crystals, KLiFe2+Al(AlSi3)O10(F,OH)2, of the mica group.(noun)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "zinnwaldite" in a sentence
"These include the cesium - and potassium-rich zeolites, pollucite and leucite, and the lithium-rich mica, zinnwaldite (a variety of the mineral lepidolite)."