W. S. Bayley — Rocks of Pigeon Point, Minnesota. 61 



phases which are found upon the contact with olivine-gabbro. 

 As has already been stated, the macroscopical and microscop- 

 ical characteristics of these rocks are such as would lead to the 

 supposition that they were produced by the mutual interfusion 

 of the basic and acid rocks at their points of contact. The 

 field relations of the three rocks leave no doubt as to the fact 

 that the intermediate rock is the result of contact action. That 

 this action took place at some distance below the surface is 

 proved by the perfect crystallization of the constituents of the 

 intermediate rock. That it was not confined to the effect of 

 solutions passing from the gabbro to the keratophyre, or the 

 reverse, is shown by the perfect freshness of the plagioclase, 

 and its well-defined crystal outlines in both rocks. 



The best place upon the point at which to study these rocks 

 is on its south side, near its eastern extremity. Here the space 

 between the fresh olivine gabbro and the typical quartz-kerato- 

 phyre is occupied by a series of rocks which exhibit in the field 

 a gradual transition between the heavy, dark basic rock, and 

 the light red keratophyre. 



Analyses and specific gravity determinations of several of 

 these intermediate products substantiate the conclusions arrived 

 at above. 



IV. Olivine gabbro, analysed by Mr. Hillebrand. 

 V. Intermediate rock (No. 11211) near the gabbro. 

 VI. Intermediate rock (N"o. 11209) midway between the red 

 rock and the gabbro. 



VII. Intermediate rock (No. 11210) near the keratophyre, 



analyzed by Mr. Hillebrand. 



VIII. Quartz-keratophyre, as given on p. 59 



SiO„ 49-88 



Ti0 2 



1-19 



Al.O, 



18-55 



Fe 2 3 



2-06 



FeO 



8-37 



MnO 



•09 



CaO 



9-72 



SrO 



tr. 



BaO 



•02 



MgO 



5-77 



K 2 



•68 



Na 2 



2'59 



Li 2 







H 2 



1-04 



PA 



•16 



CI 



tr. 



Sp. Gr. 



100-12 

 . 2-923 



V. 



VI. 



VII. 



VIII. 



50-69 



57-88 



57-98 



72-42 





. 



1-75 



•40 











13-58 



13-04 











3-11 



•68 











8-68 



2-49 











•13 



•09 



7'94 



4-68 



2-01 

 tr. 



•04 



•66 







•15 







« _ . _ 



2-87 



•58 



-~- . - 







3-44 



4-97 











3-56 



3-44 



. 







tr. 



tr. 









2-47 



1-21 



-- - 







•29 



•20 







99-91 



100-33 





2-741 





2-620 



