642 GEOLOGY OF CENTRAL WISCONSIN. 



partially dissolvecl, or replaced in part by crystalized sUica; the latter presenting' in the 

 polarized light colored patches wliich have frequently their crystallographic axes all 

 lying in the same direction. On the other hand, many of the quartz grains enclose crys- 

 tals of felspar, but these may be instances -whore the felspathic material has been 

 almost entu-ely replaced by the silica. The quartz resembles vein quartz and contains a 

 few fluid inclusions. 



1430. Quartz-Porphyry. Hukonian? From head of Lalce Buffalo, N. E. qv. 

 of Sec. 8, T. 14, R. 9. E., Marquette county. Dark reddish-brown; pnrphyritio texture. 

 The cleavage faoeis of the felspar are the only mineral ingredients that can be recog- 

 nized by the naked eye. With the microscope, the base presents a semi-granular moss- 

 like texture, in which are strewn a few crystals of orthoolase and quartz, also numerous 

 small crystal grains of magnetite. To the latter is due the dark color of the rook. 



