( 605 ) 
Colourless, very lustrous needles up to 
5 rn.ni. in length and usually flattened 
along {010}. They exhibit many vicinal 
planes particularly in the vertical zone, and 
greater angular differences occur also in 
different individual crystals. The measure¬ 
ments must, therefore, be regarded only as 
approximations. 
Rhombk-bipyra mida l. 
cubic — 0.590 :1: 0.607. 
Forms: m= {lid}, b= {010} and p=\ 120}, 
very lustrous; particulary b, which is also 
a cleavage plane and possesses a high lustre. 
On the other hand q = {011} and s= {021} 
are dull, the form {021} is mostly absent. 
The crystals exhibit a pronounced inclination 
to tetragonal symmetry. 
Measured: 
in : m = (110): (110) =* 61° 5' 
b:q = (010) : (Oil) =* 58 Uk 
m :p = (110): (120)= 19 25 
p :b = (120):(010) = 39 59 
q :q = (Oil) : (Oil) = 62 50 
m:q = (110): (Oil) = 74 54 
m : b ■ — (110): (010) = 59 274 
bis = (010): (021) = 39 46 
S .q =(021): (Oil) =19 0 
Completely cleavable towards {010}. 
The optical axial plane is {001} with the ar-axis as first diagonal. 
Strong rhombic dispersion with q <[ v; the apparent axial angle in 
cedar oil (1.51) was about 63°. 
It may be observed here that the tellurium precipitated from 
telluric acid by hydrazinehydrate is distinguished from that preci¬ 
pitated from a hydrochloric acid solution by sulphurdioxide which 
is also amorphous, by a perceptible darker colour. It is, as yet, 
undecided whether this is merely due to another degree of division 
or to a real allotropism of the amorphous modification. 
Calculated: 
19° 184' 
40 24 
62 31 
74 43 
59 274 
39 29 
19 16 
Fig. 1. 
Crystalline form of basic 
