A new phase Zn3Cu4Sb2O12 was analyzed by X-ray powder diffraction. Its monoclinic unit cell parameters are a=21.0378(19) Å, b=8.7825(7) Å, c=5.5860(4) Å, and β=112.578(7)°, and the space group is either Cc (9) or C2/c (15). From comparison with density measurements, Z=4.