( 673 ) 
Triclino-pinacoidal. 
a:b:¢=0,8072-: 1 : 0.8239 
Ai TE sist n= SPAN 
hldk Bik D= il 5 
C= 58° 35! n= (HOE 
Forms observed: «a — {100}, predominant, well-reflecting, better 
than 6 = {010}, which form is also narrower; ¢ = {OO}, very lustrous 
and well developed ; #7 = {110}, narrow but well-reflecting ; ¢ = {011}, 
narrow very lustrous; = 101}, somewhat broader and yielding 
good reflexes. 
The crystals are flattened along a and elongated in the direction 
of the c-axis. 
Measured : Caleulated : 
mer (LOO) (O01j— * Gb: B/L —- 
G20) = (100) =(O10) = 191 95 == 
b:e = (010): (001) = *100 27 = 
a:r = (100): (401) =* 50 12'/, En 
Giga (OO. (O11), = * 45,39 — 
q:6 =(011):(010)= 5444 54°48’ 
c:r =(001):(101)— 64 40, 64 40"/, 
m:b = (410):(010) = 75 23 75 19 
m:a = (110):(100) = 46 2 46 6 
P01): (01d) == 5150 51.35 
m:r = (110):(101)= 65 36 65 22 
m:q —(110):(011) = 62 54 63 3 
The crysials are very completely cleavable towards {001}; th 
plane of cleavage is very lustrous. 
On {100} obtuse-angular extinction; its amount is small, only about 
7°40' in regard to the vertical side; in convergent light a dark 
hyperbole is notieed on this plane. 
The specific gravity of the crystals is 1,696 at 12° C.; the equi- 
valent volume is, therefore, 113,20. 
The topical axes are y:wW:w = 4,8484 : 6,0065 : 55,1422. 
