100 



to be able to determine its crystalline form; its belonging to 

 the rhombohedral hemihedrism is also exceedingly little con- 

 spicuous in many of the crystals, and, as has also been pointed 

 out by Flink, it has proved to be impossible by means of 

 etching figures to form any conclusion as to the crystalline 

 form. 



The condition of the faces of the crystals here mentioned 

 is, as usually, exceedingly bad, with the exception of the base, 

 which is tolerably plane and very bright. Especially all the 

 pyramids of the first order (those corresponding to rhombo- 

 hedra) are quite remarkably uneven and opaque, so that only 

 in a few cases they have given faint reflections in the gonio- 

 meter, by which it has been possible to determine them; the 

 surfaces of t and и are somewhat more bright than all the 

 others, but not more plane; in the upper end of the crystals 

 all the mentioned faces are highly striated horizontally; in the 

 lower, pyramidal end, on the other hand, the striation dis- 

 appears entirely. The faces of the second order, о and o', are, 

 like t and г«, tolerably bright, but exceedingly uneven; they are, 

 however, not striated. They have been determined by the 

 following measurements: 



^--^- Til Variations. ^^-/Д^ 



:c = (I123):(000l)^ g^„g^, . 64°22'-68°05' 65°59'. 





o^:c^ = (I123):(000l 



The variations, as is seen, are very great, but as the 

 indices of the symbol of the surfaces are very simple, they 

 may be regarded as being determined with sufficient certainty. 



With regard to colour and other physical properties, these 

 crystals agree entirely with the hitherto known forms of the 

 mineral. They are found together with crystals of synchysite 



1) After the axial ratio: с = 3.3645ß, given for parisite by Vrba in 

 Zeitsciir. f. Kryst. 15, 1889, p. 210. 



