292 



FINLAY 



noted with (lOo) as the composition face. The twinning is 

 occasionally repeated in the same individual. 



Olivine is the only other phenocryst. (See PL XIII, fig. i.) 

 Several crystals of this mineral often grow together. They 

 almost always show corroded outlines. The inclusions are 

 augite and magnetite. 



The chief mineral of the ground-mass is a pale brown horn- 

 blende in short stubby prisms of microscopic proportions .05 

 mm. by .02 mm. These are slightly pleochroic. The basal 

 sections are eight-sided by the development of the prism and 

 pinacoid. 



The many small augites of a younger generation are by no 

 means so numerous. They may be easily distinguished from 

 the hornblendes by their buff color. Interstitial feldspar is 

 found all through the ground-mass in pieces which are too 

 small to give a clue as to their characteristics. Grains of mag- 

 netite are everywhere present and secondary analcite should 

 be noted. 



Table I 





I. 



II. 

 42.49 



III. 



IV. 



V. 



VI. 



VII. 



VIII. 



SiOg 



58.40 



62.31 



45-75 



48.03 



48.49 



52.83 



49.42 



TiO, 



.25 













.10 





AlA 



20.25 



17.68 



18.63 



18.51 



20.98 



18.99 



20.70 



22.99 



Fe,03 



1.78 



5-12 



2.38 



6.55 



7.C6 



9-59 



2.84 



2.70 



FeO 



2.41 



590 



1-33 



6.02 



4.51 



1. 00 



1.89 



1.89 



MgO 



■49 



5.28 



.60 



5.06 



4-43 



5-05 



.41 



•45 



CaO 



311 



15.81 



5-91? 



11.85 



9.54 



10.78 



1. 00 



2-59 



Na,0 



7.01 



4.29 



4-97 



3-41 



3-28 



3-47 



9^94 



9-63 



K,0 



5.39 



2.97 



3-52 



2-35 



1.99 



1.42 



4.87 



4.21 



P2O5 



.20 





.07 



tr. 







•03 





H.Ono 



.27 



.38 



.16 



.06 



.21 



.10 



■37 



.3« 



Up'sn 



•57 





.07 



.20 



.40 



•55 



5.28 



5-73 





100.13 



99.92 



99.95 



99.76 



100.49 



99-44 



99.62 



99-99 



I. Nepheline syenite. H. S. Washington, analyst. 

 II. Camptonite. G. I. Finlay, analyst. 



III. Andesite. G. I. Finlay, analyst. 



IV. Diorite. G. I. Finlay, analyst. 

 V. Basalt. G. I. Finlay, analyst. 



VI. Diorite. Diobasic facies. G. I. Finlay, analyst. 

 VII. Analcite tinguaite. H. S. Washington, analyst. 

 VIII. Analcite tinguaite. G. I. Finlay, analyst. 



