PYRAMIDAL CLASS (Hemimorphic-tetartohedral.) Here the only element of symmetry is the tetrad axis. The pyramids of the first { hhl } , second { hol } ,and third { hkl } , orders have each only four faces at one or other end of the crystal and are hemimorphic. All the simple forms are thus open forms.
Examples : wulfenite barium antimonyl dextro tartrate and iodosuccimide NI).