AM_Calciotantite Formula: (Ta2.821 Nb1.179) Ca O11 Name: Calciotantite Unit cell: 6.2261 6.2261 12.28 90.0 90.0 120.0 , V=412.25 Space group: P6322 (182)

Cooper M A , Hawthorne F C , Cerny P , The Canadian Mineralogist , 37 (1999) p.1289-1294, Ta-Nb order in the crystal structure of niobium-rich calciotantite