22 Penfeld — Interpretation of Mineral Analyses. 



at last been found: the empirical formula of the tourmaline 

 acid must be H^B^Si.^^. 



And now, for the sake of the discussion, some space will be 

 devoted to the ratios derived from the anatyses of Riggs, and 

 Jannasch and Kalb. These have already been given by Foote 

 and the author* with -^ Si0 2 as unity, and are now repeated, 

 together with the ratios derived by taking ^\ Total Hydrogen 

 as unity. They have moreover been arranged in series, com- 

 mencing with the closest approximation to 4 : 20 between SiO„ 

 and Total Hydrogen, and proceeding to the maximum devi- 

 ation from this ratio. 



Tourmaline Ratios derived 



FKOM THE 



Analyses of Riggs 



No. 



No. Dana. 



Si0 2 : 



B 2 3 



. Total H. 



Si0 2 



B 2 3 



: Total H 



1. 



43. 



4-00 : 



0-94 



: 20-03 



3-99 : 



94 



20-00 



2. 



45. 



4-00 : 



0-95 



• 20-03 



3-99 : 



0-95 



20-00 



3. 



48. 



4-00 : 



1-01 



20-06 



3-99 : 



1-00 



20-00 



4. 



47. 



4-00 : 



0'9S 



20-08 



3.98 : 



0-97 



20-00 



5. 



52. 



4-00 : 



0-94 



20-11 



3-98 : 



0-93 



20-00 



6. 



49. 



4-00 : 



1-01 



: 20-12 



3-97 : 



1-00 



20-00 



7. 



36. 



4-00 : 



090 



. 20-2 



3-96 : 



0-89 



20-00 



8. 



44. 



4-00 : 



0-88 



20-2 



3-96 : 



0-87 



20-00 



9. 



46. 



4-00 : 



0-96 



20-2 



3-96 : 



0-95 



20-00 



10. 



42. 



4-00 : 



0-97 



19-8 



4-04 : 



0-98 



20-00 



11. 



54. 



4-00 : 



0-98 



19-8 



4-04 : 



0-99 



20-00 



12. 



39. 



4-00 : 



0-94 



19-7 



4-06 : 



0'95 



20-00 



13. 



41. 



4-00 : 



0'92 



19-7 



4-06 : 



0.93 



20-00 



14. 



51. 



4-00 : 



0-91 



19-6 



4-08 : 



0.93 



20-00 



15. 



37. 



4-00 : 



0-93 



20-5 



3-90 : 



0-91 



20-00 



16. 



38. 



4-00 : 



0-92 



19-5 



4-10 : 



0-93 



20-00 



17. 



55. 



4-00 : 



1-01 



: 20-6 



3-88 : 



0-98 



20-00 



18. 



40. 



4-00 : 



0-96 



19-3 



4*14 : 



1-00 



2000 



19. 



50. 



4-00 : 



0-98 



19-2 



4-16 : 



1-02 



20-00 



20. 



53. 



4-00 : 



0-97 



18-9 



4-23 : 



1-00 



20-00 



Average 



4-00 : 



0-95 



19-88 



4-02 : 



0-96 



20-00 





Tourmaline 



Ratios 



DERIVED PROM 



THE A 



NALTS 



ES OF 







Jannasch 



and Kali 









No. 



No. Dana. 



Si0 2 : 



B 2 3 



: Total H. 



Si0 2 : 



B 2 3 



: Total H 



1. 



62. 



4-00 : 



0-80 



20-00 



4-00 : 



0-80 



20-00 



2. 



64. 



4-00 : 



0-84 



: 2001 



4-00 : 



0-84 



20-00 



3. 



61. 



4-00 : 



95 



■ 20-2 



3-96 : 



0-94 



20-00 



4. 



57. 



4-00 : 



0-99 



19-8 



4-04 : 



1-00 



20-00 



5. 



56. 



4-00 : 



0-96 



19-7 



4-06 : 



0-97 



20-00 



6. 



63. 



4-00 : 



0-98 



19-7 



4-06 : 



0-99 



20-00 



7. 



58. 



4-UO : 



0-95 



20-4 



3-92 : 



0-93 



20-00 



8. 



60. 



4-00 : 



0-88 



20-4 



3-92 : 



0-86 



20-00 



9. 



59. 



4-00 : 



0-92 



18-8 



4-25 : 



0-98 



20-00 



Average 



4-00 : 



0-92 



19-9 



4-02 : 



0-93 



20-00 







*Loc 



. cit., pp 



. 114 and 115 









