AN ANALCITE-BEARING CAMPTONITE $0? 



ing camptonite. I am indebted to Dr. Bascom for suggestions 

 on nomenclature. 



The accurate recalculation of the analysis proved impossible, 

 owin^" to the combination of minerals containing the same 

 oxides. The high Na 2 is a strong indication that the isotropic 

 constituent is analcite, and this is further indicated by the 

 optical character of the plagioclase ; it is near the anorthite end 

 of the series, hence, has low Na 2 0. Microscopically horn- 

 blende, augite, and plagioclase are present in approximately 

 equal amounts. 



Analyses two and three are typical camptonites, and it will 

 readily be seen that the Las Vegas rock is close to them chem- 

 ically. Analyses four, five and six are of rocks of other groups 

 which are also similar chemically. The likeness of the last three 

 was kindly suggested by Dr. Washington. 



I. H. Ogilvie. 



Geological Department, 

 Columbia University. 



