197 
The structure of this rock affords a beautiful illustration 
of the eflect of erush. Every grain shows evidence of pres- 
sure in the development of  undulose extinction, in- 
cipient fracture, or complete granulation. Іп spite 
of the abundance of felspar, however, there is no sericite de- 
veloped. The quartz grains are dovetailed, and not cemented 
together. In fact, there is practically no recrystallization of 
material, and this suggests that water was absent during the 
period of pressure. The production of cross-hatched twin- 
ning in a felspar as the resull of pressure is illustrated in one 
section. Тһе whole rock has a distinctly foliated appear- 
ance. The limes of inclusions in the quartz granules do not 
pass from grain to grain. 
vii Gumeracha (exact locality not known). 
Шот ов бо рас characters. Rather coarse 
framed, very distinctly schistose quartzite, of pinkish colour. 
Fractures around the grains as well as across them. Parallel 
folia differ in texture and are differently.silicified. Хо fel- 
spar noticeable. : 
Microscopie characters. —Coarser bands are 
probably due to entire recrystallization of the quartz. Strain 
structures comparatively slight, though there is a good deal 
of undulose extinction and peripheral granulation. A few 
rounded flakes of biotite are included, and lines of liquid and 
gas cavities are continuous from grain to grain. These lines 
appear to be perpendicular to the plane of schistosity of the 
rock, and therefore parallel to the direction of maximum 
pressure. The finer bands of the rock consist of completely 
angular quartz grains, whose arrangement gives a very mark- 
ed foliated appearance to the rock, but which show remark- 
ably little evidence of strain. "These bands are crowded with 
small muscovite and biotite flakes, rutile crystals (some of 
which show geniculate twinning), and zircon crystals. The 
arrangement of all of these, with their long axes in one direc- 
tion, makes the schistose appearance of the rock all the more 
striking. Some little patches of sericitic material are also 
present, but no felspar or composite grains can be observed. 
The rock, as a whole, is very porous. 
vin Mount Pleasant. 
Macroscopic characters.—Very like those 
of vi. 
Microscopie characters.—The same type of 
rock as vi., but finer in texture and more felspathic. About 
40 per cent. of the rock consists of felspar, the rest is mainly 
quartz, a little biotite 1s present. 
There is evidence of very severe crush, which has resulted 
in very extensive shattering of the quartz grains, with very 
