32 



either driisy and quite dull or else less brilliant at least than 

 the other faces of the crystals. Often they are also some- 

 what curved (convex). The faces belonging to the form о are 

 subordinate in size to those of p, but always very brilliant. 

 They lie in the zone between jj and n and are often some- 

 what striated parallel to the axis of this zone. The crystals 

 are occasionally developed at both ends. Not unfrequently 

 two or more individuals are grown together in a position not 

 quite parallel. 



The lorenzenite crystals present two types of development 

 somewhat different from each other. 



Type I. 



The lorenzenite crystals of this type are chiefly characterized 

 by their being terminated by the form j:» alone, the faces of 

 which on these crystals are always drusy and dull. A con- 

 spicuous peculiarity of these crystals is, farther, their being 

 black at the ends, while the rest of the crystal has the usual 

 appearance of the mineral, which is rather light and transparent. 

 The crystals look like small lucifer matches with dark ends. 

 The dark colour is not, however, due to any superficial coating 

 of foreign matter, as may be distinctly seen with the aid of the 

 microscope. The terminal portions of the crystals are quite 

 impregnated with the colouring matter, the true nature of 

 which cannot, however, be stated. Lorenzenite crystals of type 

 1 are represented by Figs. 1 and 2, Plate VII. 



Type 11. 



The crystals of the second type are somewhat larger in 

 size than tliose of type I. They are terminated by the pyramids 

 p and 0, ihe latter of which belongs exckisively to this tyjie 

 (Fig. 3, Plate VII). Tliey are somewhat ilattened in the direction 



