Because the presence of iron as marmatite in sphalerite may cause serious loss of zinc, knowledge of the amount of iron remaining after flotation is important. Difficulty in collecting samples of pure sphalerite made desirable application of micromethods to the analysis of six samples of sphalerite from the Kristineberg mine in Sweden, , varying in color from pale yellow to brown, the procedure used is presented here in detail. The iron content was found to vary from 1 to 8.546, corresponding to a variation of 65 to 58% in zinc content. The normal composition of sphalerite from the Kristineberg mine i s approximately 64% zinc, 9.5% iron, 0.970 cadmium, and 3370 sulfur.