96 



Fis. 1. Er i kite. 



The forms of the crystals may be seen from the annexed 

 figures ; they do not represent sharply bounded types of the 



mineral, but are connected 

 with each other by in- 

 numerable transitional 

 forms. 



The simplest form of 

 all is the one represented 

 by fig. 1. 



Combination : a (lOO), 

 o{l30}, (?{00l}, forming 

 together an almost regular 

 hexagonal prism , which 

 may generally be orien- 

 tated by the fact that the 

 prismatic faces are verti- 

 cally striated what is not 

 the case with «{lOO}. Ge- 

 nerally, however, small 

 faces are found of (^(012) 

 this being the most com- 

 mon form but three, and 

 often surpassing c(OOl) 

 in size ; the faces next 

 supervening are 5{oio} 

 and (/{02l}, when we get 

 the form shown in fig, 2. 



Most of the crystals 



are of a form very similar 



to this or occupying a 



position between this and 

 Fig. 3. Eli kite. 



the preceding one. 



To these are to be added as not very rare faces ^{lllj, 



r{lOl}, and ;h{i10), and then we get the form shown in fig. 3. 



Fie. 2. Er i kite. 



