Washington — Pyroxenite and Hornblendite in Brazil. 81 



No feldspar or apatite are to be seen and I could find no grains 

 of the pleonaste which is present in the pyroxenite. 



Chemical Composition. — An analysis was made by the usual 

 methods and the results are given below with three others of 

 closely similar rocks. 





Table I. 









A 



B 



C 



D 



Si0 2 



44-78 



44-18 



43-17 



43-51 



A1 3 G 3 



9-38 



10-67 



0-97 



10-03 



11-42 

 4-97 

 6-36 



9*82 



FeO 



4-51 



6*32 



_ 2 3 



FeO 



.... 7-70 



9-62 



MgO 



16-85 



17-77 



16-97 



14-97 



CaO 



10-85 



9-75 



11-62 



11-83 



Na 2 



2-24 



2-37 

 1-23 

 0-97 



1-11 



o-io 



2-51 



1-30 



KO 



0'20 



0*25 



H o 0+ .... 



0-25 



0-64 



h;o- .... 

 co 2 . 



0-08 







0-22 



_ _ _ . 



none 



trace 



071 



_ _ _ _ 



TiO, 



0-74 



1-30 



1-23 



1-02 



Zr0 2 



none 



.... 







. . _ _ 



PO 



none 



0-38 



0-04 

 0-06 



0*03 



s 



0-29 





CrO 



0*24 







0*14 





MnO 



1-90 



0-21 



NiO 



none 















BaO 



none 



... - 











LiO 



none 







' .... 



.... 



CuO 



0-16 















100-07 



99-83 100-63 



99-52 



A. Hornblendite fTV.l(2).3.2.2.). Near Maracas, Bahia, 

 Brazil. H. S. Washington, analyst. 



B. Kylite (feldspathic peridJtite) ((IH)IV.P.3/2.2). Ben- 

 beoch, Kyle District, Ayrshire, Scotland. M. Dittrich, analyst. 

 G. W. Tyrrell, Geol. Mag. (V), ix, p. 122, 1912. 



C. Amphibole picrite ((III) IV. (1) 2.3/2/2). Sequoia P. O., 

 Yosemite National Park, California. G. Steiger, analyst. H. W. 

 Turner, U. S. G. S. Bull. 228, p. 242, 1904. 



D. Hornblendite ("IV. "2. 3. 2. 2). Nakety, New Caledonia. 

 Boiteau, analyst. A. Lacroix, C. R., clii, p. 820, 1911. 



From the analysis it is seen that the hornblendite is very 

 fresh — remarkably so for so mafic a rock. In its general fea- 

 tures it closely resembles other hornblendites as well as some 

 peridotites which contain either hornblende or subordinate 

 feldspar (kylite). The titanium is not high, there is a little 

 chromium and copper but no nickel, while the percentage of 



Am. Jouk. Sci.— Fourth Series, Vol. XXXVIII, No. 223.— July, 1914. 



