(U 



giving very sharp reflections and easily measurable; ; / = }104j and 

 o=:{lO]|, small but distinctly reflecting; in = \()71\, very small 

 and dull. 



The habit of the crystals is elongated parallel to the r-axis. 



A distinct cleavage was not observed. 



On all faces óf the vertical zone a normal e.xtinctioii is found ; 

 no appreciable dichroism. The plane of the optical axes is jOOl}, 

 with the A-axis as first bisectrix. The apparent axial angle is very 

 small; the dispersion is strong: ? -^ '"• The birefringence is [)Ositive. 



The specific gravity of the crystals at 25° C. was : (J40 = 2.289 ; 

 the molecular-volume is thus: 278,72. 



Topical pammetevs : x : »f' : "> = «,3699 : 7,6968 : 5,6849. 



Angular Foi'tns : Ohserwd : Calculated : 



a :r =:z (100) : (102) = *65° 57' — 

 (Oil) z=*59 26 — 



p :<? = (120) 



r -.q — (T02) 



r -.p = (T02) 



a -.m^ (100) 



m:p = (340) 



p :*■ = (120) 



(Oil) = 

 (T2O) =: 

 (340) = 

 (120) = 

 (3.16.0) = 



s :b =(3.1(1.0): (010) 



r = (102) 



q = (340) 



q = (Oil) 



:q = (010) 



:t - (101) 



■.t = (104) 



a = (102) 



:a = (101) 



:w =r: (010) 



(102) = 



(Oil) = 



(OFI) =r 



(Oil) = 



(r04) = 



(r04) = 



(101) = 



(100) = 



(071) = 



42 

 77 

 47 

 U 

 18 

 12 

 48 

 63 

 72 

 53 

 11 

 25 

 17 

 48 

 10 



41 



50 

 4 

 20 

 46 

 12 

 40 

 52 

 34 

 38 

 15 

 48 

 25 

 59 



42° 44' 



77 50 



Fig. 10. 



Dextrogyratory 



Triethylenedia- 



mine-Cobalti- 



iodide. 



On {lOOj we ol)tained with mixtures of alcohol and water very 

 long, acute, hexagonal corrosion-figures and irregularly bordered 

 rectangular elevations arranged in long rows. On the other hand 

 we obtained on the faces of the prism triangular and trapezium- 

 shaped corrosion-figures, which prove<l beyond doubt the presence of 

 n horizontal syinmetry-plane, parallel to (//|001j). 



The RoNTGKNogi-am of a plate parallel to //iOülj was very irre- 

 gular and rudimentary, very probably however at least one single 

 symmetry-plane might be present. 



