146 BULLETIN OF THE UNIVERSITY OF WISCONSIN, 



est development, or a thick tabular habit with the basal 

 pinacoid the tabular face. Crystals of the first men- 

 tioned variety possess about the proportions given by Far- 

 rington for the crystals of lath-like habit from Arizona.^ 

 Different crystals show considerable variation in the oc- 

 currence of forms as well as in the relative development 

 of those which occur. 



Three crystals have been completely measured, the first 

 two being lath-shaped, but representing different combina- 

 tions, and the third tabular. In all, ten forms have been 

 determined, four of which are new to the species. 



On crystal I the prominent faces in the zone of the axis 

 b are the basal pinacoid, the negative unit orthodome 

 (^), and the new form fPco (205); and the crystal is 



terminated by a single plane of e, *P2 (2 4 5). (See plate 

 7, fig. 6.) The habit of crystal II is conditioned chiefly 

 by the same forms as crystal I, with the addition of the new 

 form IP 00 (203) in the zone of &; and though both e and 



the new form b, — |P| (9.12.8), are represented as terminal 

 planes, the former is much the larger, and one of its faces 

 is large and the other comparatively small (plate 7, fig. 7.). 

 On crystal III the terminal forms occur with their full 

 complement of faces, which have nearly equal development 

 (plate 7, fig. 8.). In addition there occurs on this crystal 

 a small positive hemi-brachypyramid, which has larger para- 

 meters on both c and a than has the form e. This pyramid 

 is not far removed from the zone of 245 and 245, but it 

 could not be accurately determined. An indeterminate 

 negative jjyramid with much rounded faces and quite 

 small development, is also found on the crystal. This 

 crystal has as the largest faces in the principal zone, 

 the tabular basal pinacoid, the form ^ , Poo (101) and the 

 new form c, — fPoo (307). The only forms which are found 



1 O. C. Farrington, On Crystallized Azurite from Arizona. Amer. Jour. Sci. (3) XLI, 

 p. 300. (1891). 



