30 Penfield and Frenzel — Identity of Chalcostibite, etc. 



Guejarite. 





Chalcostibite. 



Guejarite. 





Chalcostibite. 



Position. 





Position. 



Position. 





Position. 



b, 010 



= 



c, 001 



m, 110 



= 



d, 101 



c, 001 



= 



b, 010 



I, 230 



= 



h, 203 



h, 210 



= 



g, 201 



d, 013 



= 



w, 061 



k, 320 



= 



*, 302 



e, 011 



= 



t, 021 



At the conclusion of his article, Friedel calls attention to 

 the close similarity in the angle of his prism, m*m = 101° 9', 

 with that of the chalcostibite prism 101° 0' measured by Rose. 



In the Brush collection at New Haven, there is a specimen 

 of chalcostibite from G-uejar, which was presented by Professor 

 Groth of Munich. It is a fragment of a crystal, without 

 terminal planes, and in appearance it agrees exactly with the 

 description of guejarite given by Friedel. However, in order 

 to make sure of its identity with the material described by him, 

 it was carefully measured, with the results which will be found 

 in column IV in the table on page 34. The specimen 

 weighed a little over one gram, and the specific gravity was 

 found to be 4*959. Cumenge gives 5*03. 



Professor Groth very kindly responded to a request to sup- 

 ply us with some of this rare material for a chemical analysis, 

 and he also furnished measurements of a crystal with terminal 

 planes, belonging to the Munich collection. These measure- 

 ments were made by Mr. Schott, and are given in column Y 

 i on page 34. The habit of this 



crystal is shown in fig. 1. 



Requests for material were also 

 sent to Professor Freidel and Mr. 

 Cumenge, and they were able to 

 supply us with some of the origi- 

 nal mineral from Guejar investigated by them. That received 

 from Professor Friedel was a small fragment of a crystal, 

 weighing 0*108 gram, which corresponded in every particular 

 with that given to us by Professor Groth. Before using it for 

 analysis, however, it was carefully measured, with the results 

 which are given in column III on page 34. The material 

 supplied by Mr. Cumenge consisted of small, finely striated 

 crystal fragments which were not adapted for measurement. 

 They weighed 0*428 gram, and, before subjecting them to 

 analysis, each crystal was tested for copper so as to make sure 

 that there were no stibnite crystals amongst them. 



The results of the analyses (by Frenzel) of the specimens 

 received from Professors Groth and Friedel, and Mr. Cumenge, 

 are given below in the columns I, II and III respectively. 



