82 
Mines and Mineral Statistics^ 
stand prominently out on the exposed snrfnee of tlie roet. This white 
porpliyritic graniteweatlicrs into round-shaped bosses, whereas thefiner- 
grained eurite granite, is generally broken up into angular masses. 
The dyke c is crossed by joints bearing E. 5'^ ; it is composed of 
fine-grained eurite, containing a little mica, and irregular veins-of quartz 
and patches of quartz and felspar ; it is of much the same composition 
and structure as the granite h, and seems to branch from it. 
At tlio point marked e in the sketch the greenstone is traversed' m 
all directions by thin veins of eurite, from a mere thread up to 4 inches 
in thickness. It is evident, therefore, that the granite with its off- 
shoot c, is younger than the greenstone, aj and also, that theporphy- 
ritic granite, d, is of still later formation. 
ll<ith these granites are affected by the same systems of joints which 
I have already described in my first report. 
Throughout the district the granites greatly cliango in structure and 
composition; tlie constituent miuemls — quartz, felspar, and mica — 
presenting an almost infinite variety of admixture and colour. 
Quartz veins, occasionally several feet thick, as at the EexTin Mine, 
Middle Croelc, are frequent in the granite. The general strike of these 
is between E. 5° IN', and K'.E., while others have a meridional strike. 
The latter are often much broken I)}'" “ faults.” I give sketches of two 
instances. Fig. 8 is of one near the Cope Hardingo Mine, and fig. ^ 
near the Hex Tin Mine. 
Quartz veins ^ inch a, ordinary granite with black mica, h h, vein 
thick, faulted by joints of quartzite, 4 inches thick, faulted by joints, c dy 
traversing ordinary gra- bearing N.E. and N. 25° W. 
nite with black mica. 
