Electron-microprobe analyses across six successive sections of a single staurolite crystal show that the staurolite has three crystallographically controlled sectors, each with a distinctive content of Al, Si, Ti, Fe, Mg, and Mn. The sector distribution of elements raises the question of whether the staurolite acts as one or several phases during growth. Total analyses of the separate sectors suggest that: (i) the staurolite has tetrahedral Al substitution for Si, and (ii) the hydroxyl content varies beween sectors.