Taikanite, BaSr 2 Mn (super 3+) 2 O 2 [Si 4 O 12 ], from the Wessels Mine, South Africa; a chain silicate related to synthetic Ca 3 Mn (super 3+) 2 [Si 4 O 12 ]

The crystal structure of the title compound has been determined (space group C2, a=14.600, b=7.759, c=5.142A, β=93.25°, Z=2) and refined to R=8% for 800 reflections. The structure is characterized by vierer single chains [Si 4 O 12 ] parallel to [010], which link edge-sharing zigzag chains of MnO 6 octahedra running parallel to [001]. Open channels in the structure are plugged by eightfold-coordinated Ba and Sr. The structure is related to that of synthetic Ca 3 Mn 3+ 2 O 2 [Si 4 O 12 ], which has the vierer single chain [Si 4 O 12 ] in common