Six analyses of berthierite from various localities are quoted by Dana and show a varying composition. The analyses correspond approximately to the formulae FeS.Sb2S3, 3FeS.2Sb2S3, and 3FeS.4Sb2S3. It is considered by Dana that the variation is probably due to the impurity of the analysed material and that the composition of berthierite is probably FeS. Sb2S3. This view is supported by the examination and analysis of a specimen of berthierite from Xullarnanna, 18 miles north of Inverell, Now South Wales.

The specimen was kindly lent by Mr. G. W. Card, Curator of the Mining Museum, Sydney, for comparison with certain minerals under investigation, and measured approximately l x l x O-7 cm. It was sliced and one portion was polished for examination under the reflecting microscope while the other portion was used for the chemical analysis.