( 614 ) 
yield constant angular values and have, crystallonomically, quite the 
appearance of a well defined compound of constant composition. 
0 r 
The compound has, in moist air, a strong odour of hydrogen- 
sulphide and is decomposed by water with separation of a black 
substance which contains tellurium and sulphur. 
Triclinic-pinacoidal. 
a i b c=. 1.6835 :1 : 1*5515 
A = 109° 43' 
5 = 122° 10£ 
C = 90° 32' 
Forms observed : c = {001}, strongly predominating ‘ a = {100} 
and b = {010} equally well developed and lustrous; q = {011} and 
r = {101} quite as much developed as a and b, and yielding sharp 
reflexes; o = {112}, lustrous and fairly large; n = {012} small but 
lustrous; u? = {111}, small and subordinate, generally with but one 
plane; m = {110}, well developed and lustrous, also without the 
parallel opposite plane. 
The habit is flattened towards {001} with slight stretching in the 
direction of the 6-axis. A complete or distinct plane of cleavage 
is not found. 
The following angular values were measured: 
a = 11 3° 7*' 
£ = 124° 13' 
