16 
Keith H. Miles. 
kyaniU* and .silliiniinite. hi fad different specimens of this rock provide 
'excellent examplas of arrc'sted mineral development with the incetdion of a 
higlun' grade faci('s due to change in stability conditions during progressive 
metamorphi.sni. 
Hand specimens of this rock collected from various }>oints in the vicinity 
of the Trig. Statioji and from the western sloju's, are creamy white to gi*ey 
in colour and of varying dmisity and grain size. Coarser grained specimens 
are much moi'e foliated or schistose and have a strong knotted structui'e 
and a characteristic silky lustre on cleavage planes. The knots, presumably 
repiH'senting andahrsile crystals, are usually rounded and llattened and show 
ii}) ns slightly lighter coloni- than the foliated matrix. They may be up to 
7.5 nims. long and nearly 5 mnis. wide. The finer ginined si>eciniens are much 
more eompact and though not markedly schistose, have a tendency to cleave 
along jtarallel ]>Ianes. The andalusile knots are only revealed on ]U)lished 
surfaces and then appt'ai' as innumerable small ronndisli, light coloured 
l>atches, averaging less than 1 mm. in diameter. The material surrounding 
these knots appears dense, tine grained and siliceous. 
In one hand sj>eeimen (5084), a medium-eoarse grained schistose type, 
one can distinguish, in addition to the andalusite knots, a few small llat^ 
pearly lustred laths of kyanite np to 2 mms. long. 
^ B 
IMM 
Pig. 5. 
A. Kyaiute-beariug andalusitc-qiiartz schist (Spec. 5082) from near Trig, 
Station, Mt. Leonora. Showing part of a large granular ])orphyrohlast 
and some granulated kyanite (darker). The quartzite matrix contains 
flakes of muscovite and oriented stringers of dark carbonaceous material. 
B, Sillimaiiite-bearing audalusite-quartz schist (Spec. IT3165) fiaiin near west 
sio[)e of Mt. Leonora, Showing sillimanite in flowijig needles developing 
upon the margin of granular poikiloblastic andalusite. Black opaque 
grains are hematite altering to iiinonite, and some grapliite. 
Thin slices show a uniform porphyroblastic gneissie lexture. The 
‘‘knots^’ or porphyrohlasts consist chiefly of colourless andalusite. This 
mineral has reached only a very early stage of crystalloblastic development, 
