Formula: (Na,Ca, Vacancy)8Al6Si6O24(CO3,SO4)2.2H2O Hexagonal
Description: Cancrinite forms as both a primary mineral and a secondary alteration product of nepheline in alkaline-rich igneous rocks such as syenites.
MARATHON COUNTY: Cancrinite is found in the rocks of the Stettin Pluton west of Wausau, where it can form orange patches up to 2 cm. across (Falster, et. al., 2000). Some reported localities are:
— Found in the “core zone” of the Stettin Pluton in the SW sec. 2 T.29N R.6E (Sood, Myers and Berlin, 1980).
— Cancrinite partly replaces nepheline in syenite with perthite and sodalite in the SE SE Sec. 22 T.29N R.6E (Sood, Myers, Berlin, 1980).
— Found as an alteration product of nepheline in a syenite pegmatite with perthite, apatite and monazite in road cuts on County Hwy U, 0.5 miles east of the Little Rib River bridge in SW SW Sec. 18 T.29N R.7E (Myers, et al., 1984).
— Found in nepheline syenite with sodalite, aegirine and arfvedsonite in NE Sec. 31 T.29N R.,7E (Weidman, 1907b).