102 



PROCEEDING OF THE ACADEMY OF 



[Vol. LXXIV 



coating which is yellowish near the assay, and white farther out. 

 Globules of lead are obtained by reduction with soda in the R. F. 

 Composition. A preliminary determination of lead gave 27.78% 

 Pb. A complete analysis (shown in Table I) was then made by 

 Dr. J. Edward Whitfield on 1.25 grams of carefully selected acicular 

 crystals. It was impossible to free the needles from some sulfides 

 and quartz. The loss of 1.18% in the analysis is due to the 

 latter mineral. Column II shows the analysis after deducting 

 8.15% sulphides, and recalculating to 100%. The ratios of the 

 constitutents are shown in column III, and approximate Pb : Sb : S 

 = 2:6:11, corresponding to Pb ? Sb 6 S„ or2PbS.3Sb 2 S 3 . 



Table I. Analysis of Keeleyite 



I. Analysis of keeleyite by Dr. J. Edward Whitfield. The 1.18% loss is clue 

 to quartz. 



II. Analysis of keeleyite recalculated after deductiag 8.15% sulfides. 



III. Ratios of II. 



IV. Theory for Pb 2 Sb 6 S u or 2PbS. 3Sb 2 S 3 . 



The mineral thus belongs to the "Acidic Division" of Dana, 

 with a ratio of PbS : Sb 2 S 3 of less than 1 : 1. Although no "Acidic" 

 lead sulfantimonite has heretofore been discovered, an analagous 

 sulfbismuthite, rezbanyite, has long been known: 



Rezbairyite 2PbS.3Bi 2 S 3 



Koeleyite 2PbS.3Sb 2 S 3 



The relation of keeleyite in composition to the other lead sulf- 

 antimonites is shown in Table II, and Figure 1. 



Table II. 



Keeleyite 



Zinkenite 



Plagionite 



Heteromorphite 



Plumosite 



Semseyite 



Boulangerite 



Embrithite 



Meneghinite 



Geocronite 



The Lead Sulfantimonites 



2PbS.3Sb 2 S 3 Orthorhombic? 



PbS.Sb 2 S 3 



5PbS.4Sb 2 S 3 



7PbS.4Sb 2 S 3 



2PbS.Sb 2 S 3 



9PbS.4Sb 2 S 3 



5PbS.2Sb 2 S 3 



3PbS.Sb 2 S 3 



4PbS.Sb2S 3 



5PbS.Sb 2 S 3 



Orthorhombic 

 Monoclinic 

 Monoclinic 

 Orthorhombic 

 Monoclinic 

 Orthorhombic 

 ? 



Orthorhombic 

 Orthorhombic 



