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PETROGRAPHICAL DESCRIPTION OF SOME ‘VARIETIES OF 
GRANITE FROM NEAR OLARY, SOUTH AUSTRALIA. 
Ву W. 6. \Үоотхогсн, B.Sc., F.G.S., Lecturer in Mineralogy 
and Petrology, University of Adelaide. 
[Read September 8, 1904.] 
The rocks which form the subject of the present note were 
ecllected by my friend and colleague, Mr. W. Howchin, 
F.G.S., on a recent visit to the northern parts of the State. 
From their stratigraphical relationships he thought they 
might possibly represent the equivalents of the Таріеу в Hill 
slates in a highly metamorphosed condition. lie submitted 
them to me, with the object of obtaining evidence for or 
against such a theory. I have had some of the most typical 
varieties sectioned, and have described four of these with 
some detail. The stratigraphical relationships will be described 
by Mr. Howchin in a separate communication to this Society. 
GNEISSIC GRANITE (A) FROM HILLS NEAR KINGS BLUFF, 
OLARY DISTRICT. 
In hand specimen the rock appears holocrystalline in tex- 
ture. The general colour effect is pinkish-grey. Its most 
obvious feature is the evidence of intense strain to which the 
rock has been subjected, and which has produced an imper- 
fect foliation. The pressure has been relieved by shearing. 
The surfaces along which slipping has taken place are not 
planes, but are curved or irregular ; a large amount of mica, 
both biotite and muscovite, has been developed on them, giv- 
ing them quite a greasy lustre. With the naked eye and the 
lens there can be distinguished quartz, pink and white fel- 
spars, the latter striated, and glistening flakes of black. and 
white mica, biotite being the more conspicuous of the two, 
though the largest flakes are of muscovite. These large sur 
faces of muscovite show a kind of “lustre mottling.” 
Microscopie Characters. 
In section the texture is seen to be granitic, but the crush- 
ing has produced a complete shattering of many of the con- 
stituents, which makes the texture appear much finer than 
it must originally have been. The foliation seen macroscopi- 
cally is not quite so marked under the microscope. 
Quartz is abundant, and, as is generally the case, has suf- 
fered much more from dynamic forces than any of the other 
constituents, which, though softer, are less brittle. In ordi- 
nary light the large allotriomorphic sections of quartz appear 
perfectly limpid except for the comparatively few inclusions 
they contain. These appear to be chiefly cavities containing 
liquid, and a reiatively rather large bubble, which, in some 
cases, shows spontaneous movement. Ir. other instances the 
cavities contain only gas. Almost every grain of quartz ex- 
