102 
Rex T. Prider. 
The aiidaliisites sliow a constant variation in size and number tliroughout 
tlie band as shown in figure 9. At the bottom of the band the andalusites 
are very abundant — they project from the weathered surfaces forming 40 per 
cent or more of the exposed surface. The crystals vary in size up to 6 x 2 x 
2 cms. The prism (110) is always well developed but the terminal faces are 
very poorly developed. 
Traversing the band towards the south the andalusites become much 
smaller and less abiindant and finally disappear, the rock then being a much 
weathered reddish muscovite schist which outcrops right up to the granite 
boundary. 
K 
A^/? 7Z//? L ScfIL £ 
1 1 
1000 F'ecf 
Pig. 9. 
Cross section of upi:)cr mica schists showing distribution of nndnlusitc. 
The andalusites in the lower part of the band, as described and figured 
l)v Simpson (1928, p. 50), all show some alteration to muscovite : — 
(1) On the periphery, to a coat of small muscovite plates. 
(2) Within the crystals there is usually an irregulai- alteration to fine 
fibrous sericite. Most of the andalusites are clouded with carbon 
dust inclusions and show the typical chiastolite cross. In addi- 
tion, we Tiiay note' a peculiar feature shown by many of these 
andalusites : the arms and cleavages of the chiastolite cross are 
curved but tiie optic ori^nitation remains constant throughout the 
wliole crystal. This feature is similar to that shown by some 
staurolite and garnet crystals (Harker, 1932, p. 221) due to rota- 
tion during their growth. 
Tlie groundmass of these rocks is a ijuartz-biotite-muscovite schist. The 
biotite is completely wt'athered. It is interleaved with coarse platy musco- 
\-ite. Quartz is abundant in sTualler irregular shaped grains. Plongated 
lenticles of sericite are common. Tliis material is similar to tliat developing 
in tlie larger andalusites and it appears to result from the shearing out of 
smaller andalusites in the bas(' of the rock. 
In one specimen this sericitic^ matei’ial is present in lenticular areas with 
iri-egular inclusions of quartz. The micas are deflected arountl these knots in 
a similar manner to the deflei'titm around larger andalusite porphyroblasts. 
