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stituent; a basal section of this mineral shows the common 
hexagonal outline, the sides of which measure about 3,” in length. 
Quartz and felspar are intergrown, forming micrographic struc- 
ture. It shows no special characters beyond those noted, and is 
a typical granite, having a sp. gr. of 2°63. 
XIV. Granite (Grey), Monarto, near Murray Bridge, S.A. 
The section shows orthoclase in zoned crystals, mzcrocline with . 
the common “cross-hatching” well shown between crossed nicols. 
Some plagioclase felspar is likewise present. Quartz is fairly 
abundant and in some parts is intergrown with orthoclase, 
giving micrographic structure. Both biotite and muscovite are 
abundant and are intergrown. The biotite shows some pleo- 
chroic haloes around included crystals of zircon. Zircons are 
also present as inclusions in felspar and quartz, while apatite also 
occurs in some of the felspars. The hand specimen shows the 
rock to be fine grained and compact ; the structure as seen from 
the slide is typically granitic. 
XV.(A) Biotrre GRANITE (with Microcline and Sphene), Palmer, 
S.A. (Collected by the author.) 
This rock is a reddish granite and has a sp. gr. of 2°63. It 
consists of orthoclase, which has so intergrown with quartz in 
places as to give micrographic structure; microcline with very 
good cross-hatching visible between crossed nicols ; quartz is 
abundant and contains liquid enclosures. The felspars are 
clouded and altered somewhat. Avotite is in plenty and some 
of the pieces show pleochroic haloes around included crystals of 
zircon. As accessory minerals are present—zircon in moderate 
sized prisms ; apatite in prisms and larger sections; sphene and- 
ilmenite are pretty conspicuous, occurring sometimes together. 
The structure is quite granitic and the texture moderately fine. 
The plagioclase is, as usual, at once seen by reason of its 
prominent lamellar twinning. <A fair amount is present. 
XV. Biotire GRANITE, Kaiserstuhl, Tanunda, S.A. 
This rock is made up of the following minerals :—Quwartz 
abundant, showing micrographic structure with felspar in places. 
It forms a good “mosaic” owing to the rock having been 
crushed. Orthoclase and mcrocline in plenty; the ‘“ cross- 
hatchingin the latter is very well developed indeed. Plagioclase 
is present in fair quantity, and in places it includes mica. 
The felspars are clouded and altered. The micas present are 
biotite and muscovite, the former in excess of the latter. They 
are crushed, frayed, and bent, and the muscovite is intergrown 
with the biotite in places. 
