Citation: Mellini, M. (1982). Niocalite revised: Twinning and crystal structure Note: cuspidine structure. Tschermaks Mineralogische und Petrographische Mitteilungen, 30, pp. 249-266.
Formula: Ca7 F Nb O17 Si4
List type: noninterleaving
List: 2D
Basis: (1;0;0 0;0;1)
Dimensionality: 2
Formula: Nb2 O20 Si4 (Nb O10 Si2)
Multiplicity: 1