Cation coordinations varying from [2] to [10] & polyhedra linked in var ways; M:O = 2:3, 3:5 & similar; framework of distorted MO6 octahedra share edges & corners with other MO6 octahedra, & corners with MO4 tetrahedra; structure intergrowth of spinel-type & nolanite-type modules.2 Structures based on hexagonal close packing for O; a parameter is same, while c parameters are multiples of 4,6 (2x cation-O octahedron) & vary btw polytypes species.3