272 



University of California. 



[Vol. 3. 



The form z = f 11.10.3] approximates the form g 



14411 = 



!GS1{ (Dana) 



Measured. 



( ialculated. 



40 41 



79 48 \ 11.10.3 \ 40 15 



!441l 



38 07 



P 



79 47 

 81 12 



The forms determined by him compared with those obtained 

 by the writer, given in Goldschniidt's and Dana's orientations 

 respectively, are: 



Schaller. 



Gdt. 

 ) 320 j 

 J35lj or 

 |TT.10.3i 



Dana. 

 J 320 ^ 

 18.14.3 \ ) 8.10.1 | 

 S l(i.20.3i 



22.28.3 



Dana. 

 Gdt. Dana. 



\ 050 \ = \ 050 | 



1781) 



!44li 



f 16.16.1 ; 



[681] 



On the Clinopinacoid. — The etch figures occurring on the 

 clinopinacoid are rhombic in shape and sometimes modified by 

 another plane, as is shown in the upper figure in Fig. 3, which 

 also shows the position of the ■ 

 etch figures with reference to the 

 crystal. A few of the etch 

 figures run over on the clino 

 prism (130), the clinopinacoid 

 here shown being the negative 

 one. Strings of the etch figures 

 also occur pitching in a direction 

 opposite to that of the clino- 

 axis. 



Figures 3 and 4, Plate 27, 

 show photomicrographs of the 

 clinopinacoidal etch figures. It 

 will be noticed that there are two 

 prominent varieties, the rhombic, 

 nearly equal in the two direc- 

 tions, and then a long narrow 



form such as is shown in Fig. 3. They are all identical, as the 

 long narrow ones are simply distorted in one direction. 



The prism { 320 \ occurs on the clinopinacoidal etch figures 

 and is the only form determinable. A remarkable fact is that on 



Fig. 3. Showing the position of 

 etch figures on the clinopinacoid 

 (010) and the optical orientation of 

 the crystal. 



