A synthetic Cu-rich tourmaline crystal (Lebedev et al. 1988) consists of three different zones. Each zone was characterized by EMPA, SIMS, and single-crystal structure refinement (SREF). The first zone (which crystallized directly on the seed crystal) has the formula ~X(Na0.8□0.2) Y(Al2.0Cu0.9□0.1) ZAl6 T(Si5.1Al0.9)O18 (BO3)3 V(OH)3 W[O0.7F0.2(OH)0.1] with lattice parameters a 15.835(1), c 7.093(1) Å (R = 2.4%). The second zone has the formula ~X(Na0.8□0.2) Y(Al1.8Cu1.1□0.1) ZAl6 T(Si5.1Al0.7B0.2)O18 (BO3)3 V(OH)3 W[(OH)0.4F0.3O0.3] with a 15.824(1), c 7.087(1) Å (R = 2.3%). The third zone (highest Cu content with ~14 wt.% CuO) has the formula X(Na0.81□0.19) Y(Cu1.72Al1.21□0.07) Z(Al5.96Cu0.04) (BO3)3 T(Si5.17Al0.48B0.35)O18 V(OH)3 W[(OH)0.63F0.37] with a 15.849(1), c 7.087(1) Å (R = 2.5%). While [4]Al decreases from zone 1 to zone 3, [4]B increases (by chemistry and SREF), which could be explained by a decreasing temperature during tourmaline crystallization. Such a T-site occupancy is in agreement with the