WEIDMAN QUARTZ KERATOPHYRE OF BARABOO BLUFFS 47 



breccia and sericite schist as well as in the unaltered 

 quartz keratophyre. The porphyritic minerals are chiefly 

 the feldspars, quartz occurring very rarely in phenocrysts. 

 The few that are found are intensely corroded, and the in- 

 dications are that they were once much more numerous, 

 the rock being at this earlier period mineralogically as it 

 is now chemically a quartz keratophyre. 



Two analyses of the rock have been made, one by Prof. 

 W. W. Daniells for the State Geological Survey, the other 

 by Mr. C. P. Austin during the preparation of this paper. 

 Below are given the analyses of the Baraboo rock in com- 

 parison with quartz keratophyres from other localities. 



I. II. III. IV. V. 



71.9 

 13.4 



) 



t.6 



) 



.2 



1.0 



.2 



12.6 

 .5 



