ABSTRACTS OF PAPERS 83 



aiidesine), potash feldspar (orthoclase and microcline), pyroxene (hypersthene 

 and some augite, diallage in part), quartz, hornblende, biotite, and usually 

 considerable apatite and ilmenite or titanit'erous magnetite. Hypersthene is a 

 I)rominent mineral in each rock member of the series, and the presence of it 

 together with that of abundant apatite and titaniferous iron oxides in places 

 establishes the close petrographic relations of this large syenitic body to tlie 

 smaller one of high phosphorus and titanium-bearing rocks of the Amherst- 

 Nelson counties rutile district described in Bulletin III-A of the Virginia Geo- 

 logical Survey. 



Complete chemical analyses have been made of representative specimens of 

 the syenite collected from a half dozen or more different localities within the 

 Virginia region. The norms calculated from these analyses show that the 

 rocks are mostly alkalicalcic, belonging to tonalase, and of the sudipotassic 

 subrang harzose. Two analyses yielded norms which fixed the position of the 

 rock as amiatose and dacose, respectively, in the quantitative system. 



Presented l)y title in the al)sence of the autlior. 



PYRRHOTITE, XORITE, AXD PYROXEXITE FROM LITCHFIELD, CONNECTICUT 



BY ERNEST HOWE 



(Abstract) 



Norites and pyroxenites from I.itch field County, Connecticut, are shown to 

 contain pyrrhotite and chalcoi^yrite as constituents of magmatic origin. Two 

 periods of crystallization are recorded, the separation of the sulphides, to- 

 gether with hornltlende, biotite. and plagioclase. having taken place after oli- 

 \'ine and i)yroxeue had crystallized and had suffered partial resorption. The 

 late appearance of the sulphides in the crystallizing magma is attributed to 

 the pre.sence of mineralizers which held the sulphides in solution. The rocks 

 are compared with those associated with the copper-nickel deposits of Sudbui-y, 

 Ontario. 



I'resented in ahstract from notes. 



Remarks were iiindc liy Messrs. W. TT. Emmons and reply made by the 

 anthor. 



SOME EFFECTS OF PRESfiURE ON ROCKS AND MINERALS 

 BY JOHN JOHNSTON ^ 



{Ahstract) 



A general discussion of the .'ivailablc exiuM-liut'iital evidence beai'iiig on tlie 

 influence of pressure on the forma tioii and behavior of rocks and minerals and 

 of the conclusions which may juslitiaiily be drawn from this evidence. 



I'resentcd ill absl raci IVoiii notes. 



Iiilrixliici'd hy Arlliur I,. Day. 



VII— Bull. Geol. Sue. Am.. Vol. '_'(;. IHU 



