216 J. C. MOULDEN. 
the felspar, large crystals of cordierite have been developed, some 
of which measure from one and a-half to two inches in length. 
Right through the rock, nevertheless, cordierite occurs in greater 
or lesser amount, which fact becomes more apparent during the 
process of grinding sections for microscopical examination, for 
then, whilst the sections are still of moderate thickness, the 
mineral in transmitted light appears of a bluish or purplish-blue 
colour. In the finished section it is perfectly transparent and 
colourless, and resembles the quartz rather closely. 
The cordierite, as observed in hand specimens of the rock, occurs 
mainly in the form of irregular grains which break with a con- 
choidal fracture, and have a vitreous lustre. Their hardness is 7 
or a little over. Idiomorphic crystals do however occur—one in 
particular, on the weathered face of a boulder of the granulite, 
was eight sided and an inch and a-half long. I have also seen 
crystals of pinite, pseudomorphous after cordierite, in the more 
altered portions of the veins. The outer edge of the southern 
vein is somewhat schistose, and contains a fair amount of silli- 
manite in colourless thin prisms, transversely jointed in the 
manner so characteristic of that mineral. It is adjoined by 4 
band of schistose amphibolite’ similar to those commonly occurring 
in the neighbouring district, and which I am, after field and 
petrographical investigation, led to regard asa greatly altered . 
basic intrusive rock of the gabbro type. This band is not less 
than twenty-nine or thirty feet in width, and it contains in places 
secondary quartz veinules. 
The outer edge of the northern vein passes somewhat abruptly 
to a schistose rock containing biotite, quartz, and a good deal of 
sillimanite. It is upon this edge of the granulite that the larger 
porphyritic crystals of cordierite have been developed in conjunc- 
tion with felspar. When weathered, the former appears quite 
dull and black with numerous irregular cracks. | 
1 Memoirs Geological Survey of N.S. Wales, Geology of the Broken 
Hill Lode, etc.—J. B. Jacquet, a.z.s.m., F.G.s., pp. 53 - 56. 
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