In this paper we describe a new structural type of metaborate anion. It consists of a three-dimensional framework in which the boron atoms are situated at the vertices of a Fedorow's truncated octahedron. Each boron atom is surrounded by four oxygen atoms forming tetrahedra which are linked to form a three-dimensional anion. This type of anion, which appears in Zn 4 O(BO 2 ) 6 , is very similar to the (Al 3 Si 3 O 12 ) 3− ion of the sodalite.