48 
liEX T. Prider. 
Table V, 
1. 
2. 
3. 
SiO., 
48-88 
47-08 
48-83 
AiX).. 
16-18 
14-78 
13-46 
Fo.D, 
3-06 
1-32 
2-88 
FeO 
ll-OO 
13-80 
10-29 
-MfiO 
6-87 
7-45 
8-03 
CaO 
4-79 
4-24 
1 1 • 95 
Na.,0 
0-96 
3-10 
1-32 
K.,0 
5-32 
1-03 
0-50 

1-24 
3-89 
1-39 

0-33 
0-22 
0-08 
'i'ib., 
1-49 
2-49 
1-24 
iWn 
0-14 
0-41 
0-07 
MnO 
0-16 
0-31 
0-18 
. JlaO 
0-14 
Nil 
Nil 
Cr.,().> ... 
0-03 
NiJ 
0-08 
Fe«.> 
n.d. 
0-14 
n.d. 
100-59 
100-26 
100-30 
Analyst : R. T. Prider. 
R. T. Prider. R. T. Prider. 
1, Biotite epidiorite (20188) 
three iiudies in from edge of dyke, Roads Board 
quarry, Armadale. 
2. Chlorite-albito epidiorite, 
Armadale. 
(Quoted from Table 
III.) 
3. Pralitised <|uartz-d()lerite, 
Armadale. 
(Quoted from Table 
IV.) 
of am])hibo!(' I’rom the edget 
^ of this dyke seems to indicate 
that it has been 
entirely r(q>laced by biotitt 
and it seems most itrobable 
that end phase 
l>otassic solutions have been active in 
these narrow dykes 
There is no 
defijiite evideiU'c to say to which of the 
other type.s of basic intrusive this 
type is related but the chemical data indicate that it is most pro])ablv related 
to the chlorite-albite epidiorite. 
The ro('k from the narrow dyke in 
the slate quarry is 
very similar to 
that occurring on the edges 
of the dyke 
described above with the exception 
that it is soTiunvhat sc'histoso and very rich in biotite. 
(F ). — The quartz veim^. 
In the g’ranitie f^aioisses there are two sets of (luartz veins as described 
in the first section of this paper. So far as can be seen by microscopical 
examination these veins are similar — they apjieai’ to be replacement bodies 
in slH*ar zones in the ^’Tanitie i‘o('ks, similar to those notcal in the Darlington 
Area (CHarke and Williams, 192(), p. 174), Specimens from the north-west 
striking veins dOO yards south-west from the Narrogin Inn, show that in 
])laces it is a (piartz seidcite rock whieh in places has small ironstained cubic 
ca\'ities i‘rom which ]>yrite has weathered. Om* si)ecim<m from here con- 
tained a considerable amount of a tine acicular mineral which is developed 
in numerous small radiating clusters. These small needles are colourless, 
have straight extinction and negative elongation and ap])ear to be dravite 
similar to that described by Simpson (19dl, p. 141) from various (piartz 
veins in the gi'anitic rocks of the Darling Itange. 
The large (jiiartz outcrop near the south end. of the area may be taken 
as r(‘pr(*s(mtative of the north striking veins. At the surface it appears to 
be a (foarse grained white quartz in some places containing darker coloured 
strings of slaty material wliich under the microscope is seen to consist largely 
