BOULANGERITE, BISMUTOPLAGIONITE, NAUMANNITE 

 AND A SILVER-BEARING VARIETY OF JAMESONITE. 



By Earl V. Shannon, 

 Assistant Curator, Department of Geology, United States National Museum. 



NOTES ON THE COMPOSITION AND OCCURRENCE OF BOULANGERITE 



INTRODDCTION. 



The mineral boulangerite, a lead sulphantimonite, has long had 

 assigned to it the formula SPhS-SboSj. This is one of the simplest 

 and most probable of the lead sulphantimonites and compounds 

 showing the same ratio of base to acid are among the most numerous, 

 abundant, and widespread in occurrence of the large class of sulpho- 

 salt minerals. 



In 1875 Rammelsberg^ collected the then available analyses of 

 boulangerite and, in a discussion of the composition of the mineral, 

 showed that the analyses differed somewhat from each other, some 

 approximating the formula SPbS.SbgSg, others yielding ratios closer 

 to 5PbS.2Sb2S3, and still others approaching the composition ex- 

 pressed by the formula lOPbS.SSboSg. Quite erroneously he states 

 that the majority of the analyses given agree most nearly with the 

 formula SPbS.Sb^Sg. 



In 1899 Sjogren ^ found a mineral at Sala, Sweden, in well-devel- 

 oped crystals similar in form to diaphorite, which he referred to 

 boulangerite. Upon analysis these crystals were found to have the 

 composition expressed by the formula 5PbS.2Sb2S3. He further 

 showed that many of the earlier analyses of boulangerite agreed most 

 nearly with this formula. 



In 1917 the present writer analyzed specimens of a steel-gray 

 fibrous sulphantimonite from Superior, Montana, and Mullan, Idaho, 

 both of which gave the formula 5PbS.2Sb2S3. In rather inexcusable 

 oversight of Sjogren's work, especially since it had been made read- 



1 Rammelsberg, C. F., Handbuch der Mineralchemie, p. 99, 1875. 



» Sjogren, H. S., Geol. Foreningens Forhandlingar, vol. 19, p. 153, 1897. 



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