286 ξO (1530) and 185 ξ- (1530) events corresponding to production cross sections of 29 μband 26 μb respectively are analysed for mass, width and electromagnetic mass difference. The distribution of invariant mass errors and important systematic effects are included in the analysis. A width of 11.0 ± 1.8 MeV for the ξO (1530) and of 16.2 ± 4.6 for ξ- (1530) are obtained. The former is in some disagreement with the presently accepted value of 7.3 ± 1.7 MeV whilst the latter is the only such reported measurement to date, and these new values bring the world average value into closer agreement with the prediction of unbroken SU(3). Corresponding masses are 1532.3 ± 0.7 MeV and 1536.2 ± 1.6 MeV giving a mass difference of ∆M = 3.9 ± 1.8 MeV and lead to a world average value of ∆M of 4.3 ± 1.3 MeV. Some conclusions regarding measurement of resonant widths are made.