SYENITE AND PORPHYRY OF NEW JERSEY 585 



the type. It is certainly dosodic. We have shown here that the 

 nephehte porphyry of Beemerville is a sodipotassic rock, in no 

 important respect different from other nephehte porphyries, and 

 we can only conclude that the sample chosen for analysis by Kemp 

 was not representative. Kemp's own descriptions of the nephehte 

 porphyry show that the rock he described was not abnormally 

 poor in orthoclase. Consequently the Beemerville rock cannot 

 maintain its position as the type sussexite. Only one rock cor- 

 responding to Brogger's original definition has been analyzed so 

 far, it being the sussexite of Kuusamo, Finland, described by 

 Hackmann (see III of Table IV). As it establishes the existence 

 of the species (the existence of which may be said to have been 

 predicted by Brogger), the name sussexite should remain in use, 

 in the sense of Brogger's definition. Sussexite is essentially a 

 nephehte porphyry devoid of feldspar, or, in other words, a porphy- 

 ritic urtite. 



Rocks of the nephehte syenite family tend to lack homogeneity 

 within the mass, and too much care cannot be exercised in the 

 selection of material for analysis, which will correspond weU with 

 the material upon which the petrographic descriptions are based. 

 Another instance showing lack of correspondence between the 

 chemical analysis and the mineralogical description is the mariu- 

 polite described by Morozewicz.^ The analysis of this rock does 

 not permit of the existence of the amount of nephehte it is said to 

 contain (according to the description). 



The Beemerville nephehte porphyry has been widely accepted 

 as the type of sussexite. Iddings calculated the ratio 



Na.O+K.O 

 SiOa 



for Brogger's grorudite-tinguaite series and found that the Beemerville 

 rock, from Kemp's figures, lay upon a prolongation of the approxi- 

 mately straight line representing the series in the diagram.^ The 

 Beemerville rock, however, is not a differentiate at all, but, as we have 

 shown, a textural variant of the main mass of the nephehte syenite. 



^ J. Morozewicz, TMPM, XXI (1902), p. 230. 

 ^ J. P. Iddings, Jour. GeoL, III (1895), p. 357. 



