The space-group of columbite, obtained from the morphology, by the Donnay method (1938) is Pman, in a new setting (a:b:c= 0.4023:1:0.3580) chosen so as to comply with the convention c<a<b. In the same setting, the space-group found by x-ray methods (Sturdivant, 1930) is Pcan. The difference lies in the interpretation of the zone [100].

The classical law of Bravais does not agree with the observed facts as well as the generalized law (Donnay-Harker, 1937), which, although not perfect, is decidedly better.

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