6в 



conspicuous face is è(oio). Of the prismatic faces s{l20} is 

 most developed; Ж{110} and /i(2l0) are rather narrow. The 

 most characteristic feature of the crystals is the fact that the 

 termination is exclusively formed by P(lOl}; only in a few 

 cases are found almost microscopic faces belonging to e(02l) 

 and /"{041}. 



Type VI. 



This form is very nearly allied to the preceding one, which 



it resembles by the large and well developed crystals; as in 



the preceding type the faces are here very regular and plane, 



almost without striae. The variations 



between the individual crystals are also 



exceedingly small, and in spite of the 



great resemblance between the two types, 



no forms of transition are found. Also 



the present form has only been found in 



a single piece and in a few detached 



crystals. 



The crystals are bounded by è{010), 

 c/{l40}, 5{l20}, h{2l0], P{tOl}, w{ZO\}, 

 k[Al]}. 



The form is more compressed from 

 the side than in the preceding type, so 

 that the extent in the direction of the 

 a-axis is about as great as the length ; 

 the three prismatic faces mentioned above, 

 are about equally developed. if(ll0} is 

 sometimes found, but is rather insigni- 

 ficant. As in the preceding type small 

 faces of the forms e{02l} and /"{04 1} may also be found here. 



j: 



Fig. 7. Ilvaite, type VI. 



Type VII 

 has only been found in a few pieces; as before mentioned, some 

 crystals of type IV have also been found in a single one of 



