The Geology and Physiography of the Lawnswood Area. 
69 
Mierometric analysis of a more acid type of xeuolitli (22.517) shows 
the following composition : Oligocdase 31 per cent., (|uartz 28 per cent., 
microcline Iti.l per cent., hornblende 11.1 per cent., biotite 8.3 per cent., 
epidote 2,7 per cent., titanite 1.6 per cent., magnetite 1 per cent,, and 
apatite 0.2 per cent. 
These xenoliths are best described as adamellites and are similar in 
many respects to the xenoliths in the granite at Victor Harbour, South 
Australia described by Kleenian (Ida). 
(b) Unifunn-yraincd (jranite. 
This ditfers from the jmi'phyi’itie granite in being a iiuifurm, medium' 
grained type with no xenoliths and no * ‘ phenocrysts, ’ ’ but very frequent 
aplite and pegmatite veins. The minerals are the same as in the por- 
phyritic granite, Microcline forms clear irregular grains two to tire mm. 
in size, which poikiloblastically enclose relics of (piartz, oligoclase, and 
biotite. Micro]Hn‘thite is fretjuently deveUtped. tn one fresh looking 
specimen (22.597) tin' microcline was extremely kiudinised. Oligoclase 
(Ab, AnJ occurs in exti'emely sanssuritised grains (two to four mm.) 
considered to be relics I'roin the granite gneiss aiul also in clear grains. 
Quartz and green chlovitised biotite inclusions occur in the sanssuritised 
form. The quartz occurs iii two habits (i) small (0.1 to 0.3mm.) rounded 
inclusions in some of the microcline and oligoclase Avhich may be relies 
from the granite gneiKs, and (ii) larger, irregular, clear grains with an 
average size of tliree mm. Biotite is invariably associated Avith epidote 
and often Avith magnetite. It is a greenisb-'broAvn variety, X = light 
broAvn, Y and Z — dark green-brown to Iumjwu. This biotite may be 
developing from tiie epidote and magnet ite. jutle green auhodral, 
moderately pleochroic amphibole with an extiuclioii of about 20^, occurs 
closely associated with a micac(‘Ous mineral. The epidote, associated Avith 
biotite, is a strongly pleochroic ty})e, optically negative Avith a larg^ 2V. 
Pleoehroism is from yelloAv (Z) to colourless (V). Euhedral titanite, 
apatite, epidote, and magnetite are accessory minei'als. 
The approximate composition is mici’ocline 3.5 per cent., oligoclase 
3>0 per cent., (juartz 2.5 per cent., biotite and amphibole eight per cent., 
titanite, epidote and apatite tAvo per cent. 
(e) Granite from (tyke (22518). 
This is a light grey, tine-grained, gneissic granite which occurs as a small 
dyke intrusive into the granitic gneiss. 
The micro-structiire is allotrioinori)hie granitic Avith slight gneissosity 
due to floAvage. The minerals are .sanssuritised oligoclase, grain-size 0.5 - 1.0 
mm. ( 45 |)er cent.) ; clear microcline 0.5 mm. in diameter and rare pheno- 
crysts np to 5mm. in diameter (20 per cent.); quartz generally in very 
small rounded inclusions in the microcline and oligoclase poikiloblasts about 
0.1 to 0.2 mm. in diameter and more rarely in larger irregular grains (20 
per cent.) ; and greenish biotite associated Avith epidote (5 per cent). 
Apatite, zircon, and rutile are accessories. 
(d) Pegmatite!^ and aplites. 
Pegmatite and aplite veins are frequent in the granites especially the 
uniform granite. Pegmatite, a])lite, and quartz veins occur with less fre- 
