EL/EOLITE-SYENITE. 



l8 7 



Chemical analysis of the yellow variety of elaeolite gave the 



following results :• 



Silica 



K • • 



. 43*35 



Alumina 



. 



• 34*32 



Ferric oxide 



> • • < 



roa 



Lime 



• • < 



0-82 



Potash . 



. • 



• 5'52 



Soda . 





14/ 62 



Loss on ignition 



• • 4 



o'75 

 100-4 > 



Neglecting the iron-oxide, which is probably present as an im- 

 purity though in larger quantity than one would expect from the 

 microscopic appearance of the mineral, this analysis indicates a 

 formula of (NaK) 2 OAl 2 3 2Si0 2 with a molecular ratio of K 2 : 

 Na 2 0= 1 : 5. The lime and iron have not been considered in cal- 

 culating the formula, although it is of course possible that they 

 have in part replaced some of the protoxides and sesquioxides, as 

 the silica found by analysis is slightly higher than would be given 

 by the above formula which takes into consideration only the soda, 

 potash, alumina and silica for the molecular ratios, RO : R 2 3 : R0 3 . 



The light-grey felspar, which is associated as large crystals 

 with the elaeolite in these contemporaneous veins, was found to have 

 an average specific gravity of 2*594. A chemical analysis made by 

 my colleague, Dr. T. L. Walker, gave the following results : — 

 Silica ....... 6470 



Alumina . 



Ferric oxide 



Lime 



Magnesia 



Strontia 



Potash 



Soda 



Loss on ignition 



22*63 



0'43 



i'34 



0-49 



(?) trace 



5'86 

 602 

 0*09 



101-56 



