CORDIERITE-BEARING ROCK FROM BROKEN HILL. 215 
the quartz porphyries (elvans) of the Auvergne district in France 
and of Cornwall, from both of which localities I have gathered 
specimens. 
Field Occurrence.—I am not, at present, prepared to describe 
generally the mode of occurrence of cordierite in all of the localities 
around Broken Hill, in which I have been fortunate enough to 
find it. I propose, therefore, to take the example primarily 
referred to and describe it more in detail. About half a mile 
south-east by south from Block 14 Mine, Broken Hill, there are 
two parallel exposures of a granulitic rock which appear to be 
parallel veins, They are separated from one another by twenty- 
seven feet of a decomposed ferruginous schistose rock, highly 
quartzose, and containing also biotite and felspar. It is mostly 
covered with the surface soil, and where it shows at surface is of 
vague character. These veins strike due east and west, and are 
traceable for about three hundred yards in length. They appear 
to have a high northerly dip, as also have the other rocks close at 
hand, but these observations of strike and dip are purely local 
and are not those prevailing generally in the district, which are 
respectively north-east, and 70° to the north-west. One of these 
granulitic veins is about twenty-seven feet wide, while the other, 
the one nearest to Block 14, is somewhat less, about twelve feet. 
The rock itself is a hard, light-grey granular material, which when 
weathered, has a light reddish crust upon its exterior surface. It 
shows a tendency to concentric weathering, hence the rounded 
masses. These exposures are by no means prominent, and are 
often obscured in places by the soil. 
When a freshly fractured surface of the unaltered rock is 
examined macroscopically, it is seen to be moderately fine in tex- 
ture, and felspar, quartz, biotite, a little pyrite and cordierite are 
Visible to the unaided eye. It breaks, when in an unweathered 
condition, with a smooth and somewhat conchoidal fracture. It 
has a specific gravity of 2°66. In some parts of it large felspar 
crystals are developed, and more particularly is this the case on 
the outer edge of the northern exposure. In conjunction with — 
s 
