Penfield and Foote — Composition of Tourmaline. 107 



and without flaws. Any traces of foreign material that might 

 possibly be adhering to their outer surfaces were removed by 

 treating them for a considerable time with hydrofluoric acid. 

 The specific gravity, taken with the chemical balance, was 

 found to be 3*089. ' 



We were prepared to extend our investigation by analyzing 

 other varieties, but having completed the above mentioned 

 two and finding that the results corresponded with those of other 

 investigators, it was decided that the data which would be 

 derived from further analyses would probably add very little 

 to the knowledge which we already possess. 



The results of the analyses are as follows : 



Colorless Tourmaline, De Kalb, N. T. 



II. 



Si0 2 36-69 



Ti0 2 -06 



B 2 3 10-86 



A1 2 3 29-75 



FeO -23 



MgO 1491 



CaO 3-47 



Na 2 1-29 



K 2 -07 



H 2 2-98 



F -92 



36 



10 

 29 



14 



3 



1 



76 

 05 



77 

 61 

 21 

 92 

 50 

 23 

 03 



95 



Average. 

 36-72^-60 = 

 •05 



10-81- 



-70 = 





29-68- 



-17 = 1 



•741 "| 



•22- 



-36 = 



•006 



1492- 



-20 = 



•746 



3-49- 



-28= 



•125 y 



1-26- 



-31 = 



•040 



•05- 



-47 = 



•002 



2-98- 



- 9 = 



•331 



•93- 



-19 = 



•049 J 



'612 4-00 



154 1-01 



3-042 19*90 



O equivalent to F 



101-11 



•39 



100-72 



Riggs. 



36*88 



•12 



10-58 



28-87 



•52 



14-53 



3-70 



1-39 



•18 



3-56 



•50 



10083 

 •21 



100-62 



Brazil. 



Riggs. 



37-39 



9 ■ 



10-29 



3965 



*2'42 



1-47 



none 



•49 



J2-67 



1-71 



3 63 



•32 



100-04 

 •13 



100-61 99-91 



* Includes 0-15 per cent. Fe 2 3 . f Includes 0-25 per cent. K 2 0. 



Green Tourmaline, Haddam Neck, Conn. 

 II. Average. 



Si0 2 36-87 



37-05 



3696-5-60 = 





•616 



Ti0 2 .... -03 



•03 



•03 





B o 3 ....11-09 



10-92 



11-00-^70 = 



•157 



A1 2 3 39-53 



39-59 



39-56 -M 7 =J 



>-327 1 





FeO 2-12 



2-15 



2-14^36 = 



•059 





MnO 1-96 



2-04 



2-00-^-35-5 = 



•056 





MgO -15 



•15 



•15-f-20 = 



•008 





CaO 1-32 



1-25 



1-28-5-28 = 



•046 



)■ 3-078 



Na 2 2-13 



2-06 



2*10-i-3l = 



•068 





Li 2 1-65 



1-63 



T64-M5 = 



•110 





H 2 3-14 



3-06 



3*10-=- 9 = 



•344 





F 1-09 



1-17 



1-13-M9 = 



•060 J 







101-09 





O equivalent to 



F.... 



•48 







4-00 



1 02 



19-98 



