358 



C. A. SUSSMILCH AND W. G. STONE. 





Per cent. 



S (FeS 2 ) 



. 0-01 



Cr 2 3 



. absent 



MO and CoO 



absent 



MnO 



. 0-02 



BaO 



. 0-10 



SrO 



. presentf 



Li 2 



v a o 8 



CuO 



Per cent. 

 ... absentf 

 ... absent 

 trace* 



100-32 



Specific gravity 2*654 

 * Trace less than 0*01%. f Spectroscopic reaction only. 



Not 





Per cent. 



Quartz 



... 41-76 



Orthoclase 



... 35-03 



Albite 



... 8-38- 



Anorthite 



5-84 



Corundum 



... 0-92 



Hypersthene... 2- 69 



Class I. 



Persalane 



Order 3 



Columbare 



Magnetite 

 Ilmenite 

 Apatite 

 HoO, CO, 



etc. 



Per cent. 



1-39 

 0-46 

 0-34 

 3-45 



100-26 



Ran 

 Subi 



2 Alsbachase 

 is: 2 Mihaloae 



Magmatic name Mihalose. 



B, The Andesites. 

 In naming these rocks andesites, the writer may appear 

 to be inconsistent, because if adhering strictly to the lines 

 laid down in the description of the quartz-porphyrites of 

 this area, these rocks should also be called porphyrites. 

 These two rock types, however, possess so many points of 

 difference that it would have been confusing, particularly 

 to students, to have called them both porphyrites. The 

 rocks now under consideration, although they are intrusive, 

 have all the appearance, both in hand specimens and under 

 the microscope, of typical andesites, whereas the rocks we 

 are calling quartz-porphyrites are more inclined to a 

 plutonic than to a volcanic type. It is not unusual to call 

 certain dyke rocks andesites, as for example, Harker in his 

 " Petrology for Students," figures and describes a dyke- 

 rock from Northumberland as an augite-andesite. 



