Single crystal X-ray investigation of norsethite, BaMg(C03h: one more mineral with an aplanar carbonate group

The crystal structure of norsethite, BaMg(C03h, [a = 5.022(1) Á, e = 16.77(1) Á, space graup Rjm, Z = 3] was reinvestigated by single crystal X-ray methods working with both natural and synthetic material. The main features of an earlier structure determination using powder data were confirmed, but no significant deviation of the atomic arrangement from Rjm was found. The carbonate group is aplanar; the most probable value for the distance of the carbon atom fram the plane defined by the three oxygen atoms is estimated to be 0.044(7) Á.