64 



With this type is connected a number of smaller crystals 

 (1 — 10""°), partly placed between the larger ones, and in many 

 respects approaching as well the preceding type as the following 

 one. The form becomes broader by 6^{l40) being pressed back 

 by the other prismatic faces, £(43l} most frequently becomes 

 larger; further is added e{02l), /"{04l}, ä:{41i}, and s{l2l}. 

 The most characteristic feature of the type is always the pre- 

 sence of the form C(33l}; on the other hand а:;{2И) disappears 

 in most of the crystals. 



Type XI 



represents among all the crystals of ilvaite those richest in forms. 

 To this type belong only small crystals (I — 2""°) exclusively 

 imbedded in calcite. The occurrence is very characteristic by 

 the fact that the crystals of the immediately adjoining cavities 



where no calcite is found, belong to 

 type I. Consequently we see here 

 more distinctly than in any other 

 place the influence of the calcite on 

 the formation of the crystals. 



Combination: è{oio}, rl'^O}, 

 ^{l40}, s{t20}, Ж{П0}, Л{210}, 

 c{00l}, w{012}, ^{Oll}, s{02l}, 

 /■{041}, P{101}, o{lll}, г{121}, 

 w{l3l}, w'{30l}, ^{31l}, A;{41l}, 

 £{43l}. 



Several of the zones of these 

 crystals are striated to a very high 

 degree, which, in connection with 

 the smallness, makes the measuring 

 an exceedingly difficult matter. In 

 Fig. 12. Ilvaite, type XI. the goniometer a very large number 

 of reflexes are seen. Bv using a different incidence, and onlv 



