Late-stage volatile-rich topaz granites occur widely but sparsely throughout the southwest England Sn-Cu-polymetallic mineralized S-type biotite granite batholith. New observations from the St. Austell area have clarified field relations, and demonstrate the importance of an aureole of tourmalinization affecting both granitic and sedimentary host rocks. Topaz granite contacts are often marked by pegmatitic zones showing undirectional solidification textures and carrying vugs of quartz-tourmaline; minor intrusive sheets have symmetrical haloes of tourmalinization within adjacent host rocks. The topaz granites are mineralogically complex, containing primary topaz, zinnwaldite, or lepidolite, amblygonite (and other phosphates), and various Nb-Ta rich accessory phases, as well as...