W. T. Schaller — Dumortierite. 



217 



face is exceedingly minute and is not shown in the drawing, 

 fig. 3, A, and the reflection was poor. 



On crystal No. 4 (N. Y.) were observed two very small 

 faces, giving poor reflections. 



w 1 11 



(2) { 



83° 46' 

 83 16 



P 

 17° 54 

 17 44 



80 19 



84 17 



16 50 



17 28 



These agree approximately with the symbol {8. 1. 20} or 

 considering the form vicinal to a dome, to { 205 \ . ' 



The following table gives the calculation of the forms of 

 dumortierite based on the elements given in this paper. The 

 table corresponds to those given in Goldschmidt's Winkel- 

 tabellen. 



= 



•8897 i Iga = 



9-94924 



lga = 



0-l\2Q2\ lgb = 



9*88779 



«. 



= 1-2943 



p=-l!2S 



c = 



•6871 



Igc, = 



9*83702 lgb o = 



0-\Q29S] lgq = 



9-83702 \b 



= 1*4554 



?0 = -6871 



m| 

 No. ij ISvm. 



Sym. 1 



•> 



P 



fo 



7o 





s 



n 



i 



X 

 (Prism) j y 



d = 



- Gdt j 



Miller 















x : y 



tgp 



1 b \ 0oc! 



010 



0° 0()' 



90° 00' 



0°00' 



90° 00' 



o c 



00' 



90° 00' 







X 



X 



2 a x o 



100 



90 00 



u 



90 00 



00 



90 



00 



00 



X 







u 



3 I x2 



120 



29 07 



u 



u 



90 00 



29 



07 



60 53 



•5570 



00 



" 



4 m oc 



110 



49 01 



a 



it 



-u 



49 



01 



40 59 



1-1510 



u 



a 



5 



9 i* 



320 



59 47 



a 



a 



u 



59 



47 



30 13 



1-7170 



a 



u 



6 



n 2 x 



210 



65 23 



a 



a 



a 



65 



23 



24 37 



2-1825 



u 



" 



7 



d 40 



102 



90 00 



21 07 



21 07 



00 



21 



07 



00 -3862 







•3862 



8 



v |0 



203 



" |27 14 



1 



27 14 



« 



27 



14 



" -5147 | 



1 ! 



•5147 



The combination seen on the six crystals measured are : 



S T o. 1 



Cal. 



6, 



a, 



h 



m, 



ft 



n, 



) 



v, 



" 2 



it 



6, 



a, 



I, 



> 



# 5 



n, 



J 



— , 



" 3 



Ariz. 



J 



? 



•> 



m, 



J 



? 



< 



~, 



« 4 



N. Y. 



», 



or, 



? 



5 



9, 



5 



J 



— , 



" 5 



a 



», 



a, 



', 



5 



9, 



J 



5 



— , 



" 6 



a 



J 



a, 



i, 



> 



9, 



J 



» 



— , 



