ZINNWALDITE KLiFe+2Al(Al,Si3)O10(F,OH)2 Monoclinic

Description: Zinnwaldite is an unusual brown lithium-rich mica found in some granitic pegmatites.

FLORENCE COUNTY: Koehler (1989) reports zinnwaldite as occurring in small euhedral books less than 4.5 mm across in a complex zoned pegmatite in Fern Township (NE NE NW sec. 22 T.39N. R.17E). Associated minerals are amblygonite, spodumene, beryl and quartz.

MARATHON COUNTY: Weidman (1907) described a lithium-rich mica from a quartz-bearing pegmatite in the NW sec. 22 T.29N. R.6E., within the Stettin pluton. He called it a new species, naming it irvingite. Irvingite was later discredited as a species and the mineral described was probably lepidolite. New work suggests the mineral is actually zinnwaldite. (Falster, et. la., 2000). The mineral was found as grayish-white to bright yellow to pale pink micaceous grains up to 2.0 cm. across. The mineral also displayed a parting causing it to break into laths or needles. It is associated with quartz, K feldspar, riebeckite, aegirine, rutile, fluorite, pyrochlore and zircon.

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