Pen field and Fremel— Identity of Chalcostibite, etc. 27 



Art. IV. — On the Identity of Chalcostibite ( Wolfsberglte) 

 and Guejarite, and on Chalcostibite from Huanchaca, 

 Bolivia; by S. L. Penfield and A. Frenzel. 



Introduction. — In December, 1894, Mr. Thomas Hohmann, 

 mining engineer at Valparaiso, Chili, sent to one of us (Frenzel), 

 for examination, some specimens, from the Pulacayo mine, 

 Huanchaca, Bolivia. Upon one of these were some prismatic 

 crystals of a mineral with metallic luster, which, we were 

 informed by Mr. Hohmann, was found very sparingly, was 

 unknown to him, and might possibly be new or worthy of 

 investigation. As the material was limited, it was decided to 

 identify the mineral, if possible, by its crystalline form, and, 

 upon examination, it was found that the cleavage and some of 

 the prominent crystal forms corresponded to the rare mineral 

 guejarite, described by Cumenge* as having the composition 

 Cu 2 S . 2Sb 2 S 3 . 



About the same time that this material was sent to us, a 

 second specimen from Huanchaca was received at the Minera- 

 lien Niederlage at Freiberg, Saxony, and Herr Zinkeisen, 

 director of that institution, on learning that the mineral had 

 been identified as guejarite, sent the specimen to Mr. L. 

 Fletcher of London, and it was purchased for the mineral col- 

 lection of the British Museum. In order to identify this 

 mineral with certainty, Mr. Fletcher requested Mr. L. J. 

 Spencer, of the Mineral Department of the British Museum, 

 to examine the crystals, when it was found that the forms 

 agreed not only with guejarite, but equally well with chalco- 

 stibite (wolfsbergite). An article was accordingly prepared by 

 Mr. Spencer " On Wolfsbergite from Bolivia ; and the probable 

 identity of Wolfsbergite and Guejarite,"f but on learning that 

 we were engaged in an investigation of the same mineral, Mr. 

 Fletcher called our attention to the fact that guejarite could 

 not be distinguished crystallographically from chalcostibite. 

 He also requested Mr. Spencer to send the results of his 

 investigation to us, in order that his results might be incorpo- 

 rated with ours, and in subsequent pages it will be shown that 

 guejarite, which has been considered as having the composi- 

 tion Cn 2 S . 2Sb 2 S 3 , is really identical with chalcostibite (wolfs- 

 bergite), Cu 2 S . Sb 2 S 3 . 



Chalcostibite from Wolfsberg in the Harz. — Upon material 

 from this locality, the species was first founded in 1835, by 

 Zinken,^: the mineral being called by him Kupferantimonglanz. 



*Bull. Soc. Min. de Prance, ii, p. 201, 1879. 



f Read before the Mineralogical Society of London, April 14, 1896. 



\ Pogg. Ann., xxxv, p. 357, 1835. 



