23 



or veins, sometimes evidently filling cracks in the felspar; in 

 other cases the vein-filling was of chlorite alone. Here pos- 

 sibly the albite was of intratelluric crystallization, and had 

 been dislocated during injection of the magma, and before the 

 final consolidation of the rock. The chlorite was often 

 crowded with rutile prisms to such an extent as to negative the 

 supposition that these had been formed by the decomposition 

 of a titaniferous biotite. 



Although it is evident from the chloritization of the mica 

 that this rock has been somewhat altered, still the effects of 

 this alteration have been reduced to a minimum since ferro- 

 magnesian constituents are so subordinate, and the analysis 

 is of interest and of some value: — 



I. 



SiO, ... 64-60 



AU63 ... 20-37 



Fe.03 ... 0-31 



Feb ... 0-67 



MgO ... 1-15 



CaO ... 0-41 



Na.O ... 9-94 



K.6 ... 0-16 



H.0+ ... 0-85 



H.O- ... 0-15 



Tib. ... 1-04 



CO,' ... tr. 



P.O. ... 0-22 



FeS. ... abs. 



ZrO. ... 0-03 



BaO" ... abs. 



CI ... — 



Total ... 99-90 



Sp. gr. at 23°C 2-635 



Albite mica syenite, 

 Browne. 



66-13 

 19-92 

 0-60 

 0-19 

 0-12 

 0-57 

 10-83 

 1-02 

 0-30) 

 0-14/ 

 0-31 

 0-40 

 0-09 

 0-05 



0-03 



100-70 



III. 



66-09 



18-85 



0-91 



1-53 



1-09 



10-84 



0-48 



1-17 



0-23 



101-19 



Rosetta Head. Anal. W. R. 



the 



II. Albitite, Sec. 40, Hundred of Roberts, Eyre Pen. 

 Anal. W. S. Chapman. Geol. Surv. of S. Austr., 

 Bull. 3, p. 16. 



III. Albitite. Koswinsky Kamen. Quoted in Rosen- 

 busch's • Elemente der Gesteinslehre," p. 263. 



The analysis shows that the felspar is a pure albite, all of 

 lime belon^ins to apatite, and the small percentage of 



potash being quite probably contained in muscovite and in 



