Existing polarized neutron diffraction data on anhydrous copper sulphate has been reanalysed. Covalence of about 23(5)% is observed. The spin is delocalized predominantly along the shortest Cu-O(3) bond, reaching the S atom. This provides a pathway for the antiferromagnetic interaction. The copper site configuration in this Jahn-Teller distorted ion, with two bonds much longer than the remaining four, is dominated by the population in the 3d(x²-y²) orbital, as expected, but a significant mixing with the 3d(z²) orbital is also observed. Model DV-X_alpha calculations support these conclusions. A contraction of the copper 3d spin density in real space is observed, which is at least partly due to spin polarization, an electron-electron correlation effect.