AMI'HIBOLITES AND RELATED R<" K III I U KLL. 265 



that these large crystals have developed during tin- re-crystallisation, under the 

 rnn-litions of the formation of the amphibolic. Tin- ;i.l>sence of any relic structure is 

 important negative evidence that these porphyroblasts were not phenocrysU in the 

 original igneous rock. 



A sample of the porphyrohlastic felspar was separated and freed as far as 

 po>sible from the ferromagnesian inclusions by hand picking and by the use of heavy 

 solutions. The sample was then analysed by Mr. .1. ('. Watson in the Victorian 

 Survey Laboratory. 



SiO 2 45-1CJ 



A1 2 3 35-34 



Fe a O a 1-05 



MgO ... str.tr. 



CaO 16-39 



Na 8 O '1-70 



K 2 -20 



H 2 -33 



H a O -00 



100-93 



This analysis demonstrates the highly calcic nature of the porphyroblast which 

 approximates to AbjAn,,. 



Specimen No. 547 is a remarkable quartz-pyroxene-amphibolite. It is distin- 

 guished as one of the very few specimens occurring on the moraine with a weathered 

 crust. It is a heavy basic rock, and a rough determination of its specific gravity gave 

 3-25. It is rather coarse-grained, and possesses a slight schistose character. In 

 section it is found to be similar in structure and character to the other specimens of 

 pyroxene-amphibolites, except that the felspar is completely replaced by quartz. The 

 amount of quartz is approximately the same as the amount of felspar in the typical 

 amphibolites. No garnet is present in the section, but grains of ilmenite and pyrite 

 are unusually abundant, and partly account for the high specific gravity. 



The Meso division of the amphibolites is more typically represented by a number 

 of amphibolites and biotite-amphibolites which are similar to some of the occurrences 

 tu at Cape Denison. In the typical examples the plagioclase is clear and often 

 untwinned, and in Nos. 946 and 959 the hornblende crystals contain numerous clear 

 inclusions of felspar and quartz, producing a "sieve" structure. In another case, 

 No. 865, there are numerous porphyroblasts of felspar, which average about 5 mm. 

 in width. This specimen was part of a large erratic in which the porphyroblasts were 

 arranged in a. linear manner and parallel with the schistosity an occurrence in strong 

 contrast with the scattered occurrences of metamorphic xenoliths in the amphibnlite 



