FOYAITE-IJULITE SERIES OF MAGNET COVE 



6og 



I. Pulaskite, Fourche Mountain. Washington, analyst. 



II. Pulaskite, Fourche Mountain. Brackett, analyst. Williams, op. cit., p. 70. 



NagO : K3O is about the same in both, being 1.57 in I and 1.66 

 in II. The specimen analyzed by Brackett apparently contained 

 a little more acmite, though the variations are scarcely more 

 than are to be expected in dii^erent specimens from the same mass. 

 Analysis I can be calculated out as below. There is appar- 

 ently an excess of AlgOg, amounting to about 4 per cent, in 

 this, as well as in II, which it is difificult to account for. It does 

 not seem to be due to kaolinite or hydronephelite, as the rock 

 is too fresh, and there is no muscovite present. Such an excess 

 of AI3O3 above (NagO + KgO) — FcgOg may be observed in 

 many analyses of nephelite-syenites, if the Fe^Og is calculated 

 as acmite, and no anorthite molecule is assumed to be present. 

 Among these are some by Hillebrand, and there is no reason to 

 suppose that this peculiarity is due to errors of analysis. It is a 

 feature of this group of rocks which seems to call for investiga- 

 tion, and may possibly be connected with the occurrence of 

 corundum in the nephelite-syenites. 



Orthoclase - - - - - 35.1 



Albite ------- 39.8 



Nephelite ------ 3.1 



Sodalite - - - - - - 1.2 



Aegirite ------ 5.1 



Hornblende, diopside, and biotite - - ii.o 



Apatite ------ 0.5 



Extra alumina ----- 4.2 



100. o 



