364 



LEDOUX: AURICHALCITE 



slides. One obtains then a great number of small individuals of 

 various forms, the most common of which is triangular in out- 

 line (fig. 1). The angle a is very acute, while the angle GHI is 

 90°. In several individuals from Big Cottonwood Canyon the 

 value of a is 19°, a value agreeing with that obtained by Pro- 

 fessor Cesaro 8 on the crystals of Flemalle. Other forms ob- 

 served on these specimens are shown in figure 2. Most of the 



(OOP 



(O'O). 



(oio) 



+ 



(too) 



.(OIO) 



(OCT) 



d 



(OOI) 



Fig. 



individuals are cleavage plates with a contour of pinacoids and 

 domes belonging to the zone (001) (010). If (Okl) is the nota- 

 tion of one of those domes, the angle a = (Okl A 010) may be 

 deduced from the equation: 



I 



k 



= c. tan 



a 



As the angle a = (013A010) has the same value of 19° as that 

 given by Professor Cesaro we may use the same parameter, 



c = 8.71263 

 log c = 0.94015. 



Table 1 gives the different a angles observed on the crystals 

 and the corresponding symbols of the domes; but the results 

 are only approximate, as the angles were measured with the 

 microscope. 



s Loc. cit. 



