Comparison of chemical analyses of actinolite asbestos carried out with EDS versus WDS reported on a diagram (Si _apfu vs Mg/Mg+Fe²⁺). The calculated uncertainty of the WDS measurements on the Mg/Mg+Fe²⁺ ratio is negligible, on S _iapfu it is plus or minus 0.3%, with the EDS it is 2.4% on both values. The WDS measurements are represented by a line, the EDS measurements by a rectangle whose sides are proportional to the uncertainty.