Gahnite and columbite with compositions (Zn5.96Fe1.55Mg0.21Mn0.13)Σ7.85Al16.09O32and (Nb7.36Ta0.60Mn2.95Fe0.98Ti0.09)Σ11.98O24occur as accessory phases in a highly evolved garnetiferous muscovite alkalifeldspar granite. Both phases have developed as a result of a concentration of Zn, Nb, and Ta during the fmal stages of the fractional crystallization which led to the formation of the pluton, and the lack of a major mafic mineral such as biotite, in which these elements are normally camouflaged in granitoid rocks.
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A. J. Tulloch (1981) studied this question.
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