MAGNETITK (JAKNET ROCKS- roU.suN. 293 



iilinost wholly contained in tin- mini and the lime in the felspar and apatite. Practically 

 no lime and magnesia is available for the garnet. In No. 102, which contains 40-8 per 

 i cut. of garnet, it can he clearly inferred that the garnet is an iron-alumina variety. 

 In No. 181 there is 4-12 percent, of MnO which probably replaces part of the FeO in the 

 garnet. No. 348 contains an exceptional amount of 8-23 per cent, of manganese and 

 the composition of the garnet may approach that of spessartite. Qualitative tests 

 indicate the presence of considerable manganese in the chlorite magnetite schist 527A 

 and in the magnetite garnet schists and gneisses Nos. 304, 814, 245, and 288. Rutile is 

 recorded in Nos. 181 and 102 and may account for part or all of the titanium content. 

 Qualitative tests revealed a fair amount of titanium in the similar rocks Nos. 245 and 

 288, but it proved to be absent in Nos. 304 and 814. In No. 245 the titanium 

 percentage is ascribed to ilmenite. 



Comparison with the chemical analysis of the Broken Hill rock shows great 

 similarity. The lower silica and higher total iron of the Broken Hill rock corresponds 

 with lower quartz and garnet percentages and higher iron ore than No. 102. Its high 

 manganese content is a marked point of resemblance with No. 348. It is distinct > 

 however, in its high lime and phosphorus which correspond with the measured percentage 

 (14-2) of apatite. Its large excess of Fe 2 O 3 over FeO appears to indicate more hematite 

 than in the Antarctic types. 



4. SUMMARY OF PETROGRAPHICAL CHARACTERS. 

 The following rocks have been described : 



Magnetite-schists Nos. 765, 912, 294. 



Biotite-magnetite-schist No. 926. 



Chlorite-magnetite-schist No. 527 A. 



Mica- magnetite-schists Nos. 55, 933. 



Mica-magnetite-gneiss ... ... ... No. 576. 



Quartz-magnetite-schist No. 296. 



Epidote-magnetite-schist No. 989. 



Magnetite-garnet-schists Nos. 889, 147, 245. 



Magnetite-garnet-gneiss Nos. 827, 181, 149, 304, 814. 



Garnet-magnetite-schists Nos. 288, 348. 



Quartz-garnet-magnetite rock No. 102. 



Quartz, felspar, and mica are the chief minerals present in the rock suite in 

 addition to the abundant magnetite and garnet which characterise the group. The 

 quartz usually shows strain polarisation colours and a cataclastic structure. In a ; * 



number of cases minute inclusions have a definite alignment within the individual quartz 

 crystals which is generally parallel to the planes of schistosity. 



