Corundum-bearing rocks are associated with metamorphosed mafic rocks in a metamorphic terrane mainly of metasedimentary rocks including gneiss, schist, amphibolite, and minor iron formation. Granulite(?) facies metamorphism of an aluminous sediment produced biotite syenite gneiss; next, perhaps late in this phase, unoriented corundum crystals surrounded by alkali feldspar halos formed by replacement of the gneiss with the addition of Al and K. The final step was local development of muscovite-sillimanite schist probably during almandine amphibolite facies metamorphism, Petrographic and minor element studies are presented in support of these conclusions.

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