JR. B. JRiggs — Composition of Tourmaline. 



45 



Pierrepont, St. Lawrence Co., IS". Y. Perfect black crystals, 

 in calcite, fuses easily, (t. 3*08. 



JVantic Gulf, Cumberland, Baffin's Land. A large black 

 crystal, easily fusible. G. 3'095. 



Stony Point, Alexander Co., N. C. Perfect medium-sized 

 black crystals, with implanted crystals of quartz ; associated 

 minerals chiefly quartz, muscovite, apatite, rutile, beryl and 

 spodumene, fuses easily. G. 3 13. 



Haddam, Ct. Black crystals in quartz and feldspar, powder 

 blue black, easily fusible. 





Pierrepont. 



Nantic Gulf. 



Stony Pt. 



Haddam. 



. 



I. 



II. 



I. 



II. 



I. 



II. 





I. II. 



Si0 2 



35-61 





35-34 





35-56 





34-95 





A1 2 3 



25-29 





30-49 





33-38 





31-11 





Fe 2 3 



•44 





none 





none 





•50 





FeO 



8-19 





8-22 





8-49 





11-87 





Ti0 2 



•55 





•40 





•55 





•57 





P 2 5 



trace 





none 





? 





trace 





MnO 



trace 





trace 





•04 





•09 





CaO 



3-31 





2-32 





•53 





•81 





MgO 



11-07 





7-76 





544 





4-45 





SrO 



none 





trace 





none 





none 





BaO 



1 





? 





none 





none 





Li 2 



trace 





trace 





trace 





trace 





Na 2 



1-51 





1-76 





2-16 





2-22 





K,0 



•20 





•15 





•24 





•24 





H 2 



3-34 3-30- 



-3-37 



3-60 3-53- 



-3-67 



3-63 3-57- 



-3-69 



3.62 



3-58-3-66 



B 2 3 



10-15 10-00-10-31 10-45 10-30-1060 1040 





9-92 9-74-10-10 



B 1 



•27 





none 





none 





none 

 100-35 







99-93 



100-49 



100-42 





Less oxygen, 



•11 

















99-8.2 



Mr. W. E. Hidden very kindly furnished the Stony Point 

 material. For the other specimens I am indebted to the 

 National Museum collection. The gravity determinations of 

 the Pierrepont, Stony Point and Nantic Gulf tourmaline were 

 kindly made by Dr. William Hallock. 



From the above analyses it is at once apparent that we have 

 three types to deal with., lithia, iron and magnesia tourmaline 

 respectively, with an indefinite number of intermediate products. 

 As an aid to comparison I have brought these results together 

 in the following table, arranging them so as best to show how 

 these types graduate from one into the other, beginning with the 

 lithia . tourmaline and passing from them through the iron 

 varieties to those of the purer magnesian type. The iron tour- 

 maline appears to be the connecting link. 



