246 WRIGHT—CRYSTALLOGRAPHIC PROPERTIES. [June 1, 
Element : eS 1.0206 
@:Cyg9= 1 : 0.8838 
a: gy =I: 1.531 
Forms : (MMP ETT (5) ea ey ea TAY OF) OCS 2 q(?) 
Bravais,..... OOOI I07O 404I 2031 IOTI 40g3 2023 50512 
BRGD aie Sis. oc fo) fe) 2 4 2 5 
oss 4 fe) 10 : Z0 50 
ARGENTODOMEYKITE. 
The crystals of the artificial argentodomeykite belong also to the 
holohedral division of the hexagonal system. Four crystals only 
were measured, each crystal exhibiting slightly different elements, 
due probably to a varying percentage of silver. For the form 2, 
20 of the several crystals 
The angle p = 65° 14’ + 29’, py = 2.167 + 0.047, in the first crystal. 
p = 65° 08/ + 20/, p, = 2.158 + 0,032, in the second. 
p = 64° 33/ + II’, py = 2.101 + 0.017, in the third. 
p = 64° 36/ + 15’, p) = 2.106 + 0.024, in the fourth. 
Although the above quantities vary considerably, still they show 
clearly that the entrance of the silver in the domeykite crystal par- 
ticle causes a change in its elements, the pyramids becoming steeper. 
Fig. 6. 
The quality of the faces of these artificial crystals was so poor that 
the influence of the silver in per cent. could not be determined. 
Size of crystals and character of faces similar to domeykite. Of 
the pyramids the form Z, 20 predominates, the form v, 10 occurred 
but once, while A, 3 0 was not observed. The face /, 20 frequently 
exhibits a slight cylindrical rounding, the axis of which runs par- 
allel to the basal edge. Its reflexion signal is then a short light 
band, its bright central part indicating the position of the face. The 
faces are invariably striated horizontally. The different types of 
