W. H. Hobbs — Goldsehmidtite, a New Mineral. 361 



which is a close approximation to Au 1 Ag 2 Te 3 . The mineral 

 krennerite contains silver in about this proportion (19 44: per 

 cent), but the proportions of gold and tellurium do not corre- 

 spond. 



Crystallography of Goldschmidtite. 



As already stated, the chief difficulty encountered in measur- 

 ing the crystals has been their minute size and the conse- 

 quently small amount of light reflected from their faces. A 

 number of the better faces afforded single images of the signal 

 so that in the prism zone, where the faces were largest, con- 

 secutive readings from the same angle showed variations of less 

 than a minute of arc, and on the best crystal the four similar 

 angles between prism and pinacoid were respectively : 



61 c 



' 42' 



61 



46 



61 



46| 



61 



m 



Considerable confidence is therefore placed in the correct- 

 ness of the constant which was determined from the angles in 

 this zone, while the values of the other constants are correct 

 only within limits of error which are sufficiently indicated by 

 a comparison of observed and calculated values of readings of 

 interfacial angles. Five crystals have been completely meas- 

 ured and particular angles have been measured also upon other 

 crystals. 



The symmetry of the mineral is easily determined as mono- 

 clinic, and it is probably also clinohedral. The principal zones 

 of the crystal are those of the axes 6 and ~b, a single clinodome 

 and a pyramid which was too small to be determined being the 

 only faces not included in these zones. Owing to the frequent 

 absence and the small development when present of the basal 

 pinacoid, the angle /3 was determined from the mutual inclina- 

 tions of the positive and negative unit orthodomes and found 

 to be 89° ll 7 . The axial ratio a : 6 : c is 1-8562:1: 1-2981. The 

 crystal forms observed number twenty-two, and are as follows : 



Zone of d— a (100) i-i ; b (010) i-l ; m (110) I; /(210) i-l\ 

 g (310) i-3 ; t (370) £f; I (130) i-3. 



Zoneofb.— y (508) — f-*y s (101) — 1-2 y n (201) —2-1; r (703) 



— -j-iy w (401) — 4-1; q (801) —8-^; x (IO'0'I) — \0-l_; v (35-0-1) 



— 35-i; £(101) 1-5 y A^(201) 2-5 y TF(401) 4-i ; X (IO-0'l) 10-i; 

 Z(14-0-l) 14-2 y c (001) O. 



Zone of d.—k (032) f-i 



The more important angle readings from which these deter- 

 minations were made are as follows : 



