42 



R. B. Riggs — Composition of Tourmaline. 



thoroughly intermingled in nearly equal proportions. One of 

 these minerals is micaceous in structure, with strong double 

 refraction like dam on rite, which it closely resembles in general 

 appearance. The other mineral is clear, colorless and apparently 

 monoclinic, with a rather low index of refraction and moderately 

 intense double refraction." 



While the Hebron rubellite alteration product retains its 

 crystalline form, its material is altered into a softer mineral of 

 an opaque talcose appearance. The analysis shows the change 

 to be toward damourite (F. W. Clarke, this Journal, .Nov., 

 1886), and not lepidolite as has been supposed in this case. 



Brazil, Calhas, Province of Minas Geraes. The association of 

 these tourmalines I was unable to find out. From their compo- 

 sition however it is probable that it does not differ greatly from 

 that of the Maine varieties. The specimens analyzed were from 

 the hands of Mr. Gr. F. Kunz. A. The pink, almost colorless 

 center of crystals having a green border, infusible, Gr. 3 "028. 

 B. Pale green, like the border of B, infusible. C. Olive 

 green, fusible in very thin splinters. D. Black, in thin splin- 

 ters a smoky blue green, fuses easily, Gr. 3"20. 



A B C D 





1. 



n. 





I. II. 





I. II. 





I. II. 



Si0 2 37-19 



— 



37-12 



37-39 



— 37-31 



36-91 





34-63 



— 34-50 



A1 2 3 42-43"] 







39-65 " 



| 



38-! 3 





32-70 





Fe 2 3 none ! 

 FeO -52 [ 







•15 



I 



•31 





-31 





42-94- 



[42-30-42-38 



3-19 





13.69 





P 2 5 nonej 







trace 



1 



•11 





none 





MuO -79 







1-47 ' 





2-22 





•12 





CaO -57 







•49 





•38 





•33 





MgO none 







none 





•04 





2 13 





Li 2 173 







1-71 





1-61 





•08 





Na 2 2-24 







2-42 





2-70 





2-11 





K 2 -23 







•25 





■28 





•24 





H 2 390 



3-86 



-3-93 



3-63 



3-60-3-66 



3-64 





3-49 



3-42-3-56 



B 2 3 10-06 9-96- 



■10-16 



10-29 



10-10-10-49 



9'87 



9-85-9-88 



9-63 



9-55-9-70 



F trace ? 







•32 



— -41 



■14 



- -17 



■06 



— -10 



99-66 







100-06 





99-53 





99-52 





Less oxygen 







•13 





•06 





•02 





99-93 



99-47 



99-50 



Dekalb, St. Lawrence Co., 1ST. Y. Colorless to light brown 

 translucent crystals, in calcite, with quartz and titanic oxide in- 

 clusions, easily fusible, Gr. 3*085. 



Gouverneur, St. Lawrence Co., K". Y. Brown, massive, asso- 

 ciated with calcite. Easily fusible. 



Hamburg, ~N. J. Large cinnamon-brown crystals, associated 

 with quartz and colorless mica in calcite, abounding in inclusions 

 of small black scales of titanic oxide. Easily fusible. 



