Pale aggregate of small yellow flakes of cookeite with muscovite, quartz and alkali feldspar. Strickland Quarry, Portland, Connecticut. Scale is in centimeters. (Photo by W. Cordua.)

Formula: LiAl4(AlSi3010)(OH)8 Monoclinic


Cookeite is a rare alteration product of other lithium minerals found in complex granitic pegmatites.

MARATHON COUNTY: White micaceous material found in a pocket in a pegmatites in the Wausau pluton, has been tentatively identified as cookeite by Falster (1987).