Niocalite is monoclinic with a=10.83, b=10.42, c=7.38 Aa, and beta =109 degrees 40'. On the basis of 2 chemical analyses, the generalized formula is (Ca,Nb) 16 Si 8 (O,OH,F) 36 . The similarity of niocalite to woehlerite, hiortdahlite, and livenite is discussed.

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