18 
Keith R. Miles. 
MT. KENNETH, YALGOO GOLDFIELD. 
Field ocviir-rence. 
Another interesting metamorphie which bears a general resemblance to 
the Camel Humps and Mt. Leonora rocks, comes from several low rocky 
rises at about s(n'en mih's easLsoutheast of Mt. Kenneth, near the eastern 
boundary of the Yalgoo Goldfield. This occurrence was described by H. W. B. 
Ta.Il)ot in IlHi) (14) and a chemical analysis, and l)i’ief petrographical 
des('i'iplion by H. A. Eanjuharson, were also published, 'flie field relations 
of tiiis rock are rather obscure, but it is appartmtly eiiciosed and presumably 
intruded by granite. 
Fetrography. 
The rock is pale greenish in colour, is medium grained and has a typical 
eveiL gTanulated schistose appearance, but has not the mai'ked knotted, or 
porphyroblastic structure of the two rocks described above, and hand speci- 
mens ai)i>ear to consist chiefly of Cjuartz and chlorite. 
The mici’osco})e, however, reveals the presence of numerous ragged prisms 
and ii‘i-(*gular, j-ather fragmentary crystals of typical kyanite showing usual 
high I’elief, good (100) cleavage, modeimte birefringence and positive ('lon- 
gation, with charactenstic maximum extimdion and negative acute bisectrix 
figure obtained from broad sections cut parallel to (100). These crystals 
are occasionally enclosed by and appanmtly de^■eloping from chlorite and 
sericite flakes, ot‘ are scatlered in groups in random orientation through an 
iri'Cgular cataclastic granidar matrix of quartz, and irregular’ I’agged plates 
of chlorite and muscovite. 
The most common accessor\ mineral in this rock occurs in small irregular, 
rather pointed prisms and rounded granules, scattered liberally throughout. 
Ihese are pleochroic in dark yellow-brown to red-})rown coloni’s, maximum 
absorption being pai’allel to the longest axis. Itelief is very high, surfaces of 
these crystals having a stippled appearance. Birefringence appears weak, 
and interferema* colours are mostly masked by absorption. Extinction is 
straight. A few gi'ains show ajij^arent development of penetration twins. 
Gi'ains were too small to give an interference ligure. They liav(‘ the colour, 
general form and extremely high refringence of ])ero\'skite, ((’aTiO;;) whilst 
the ])leochroism am! extinction suggest either brookite, (TiO,), or the meta- 
mori>hic mineral staurolite (hydrated silicate of Fe and AL). The entire 
absence of CaO in the chemical analysis of this rock (C) rathei’ dis])oscs of 
th(‘ possi])ility ot perovskite. The gc'iu'ral distribution is that of a detrital 
mineral and brookite is suggested. 
Other accessories inelmie clear yellow-brown rutile in euhedral })risms, 
pale yelloAV zix’cons often producing ]>leochroie haloes in chlorite, broken 
apatite needles, and a few grains of cloudy felspar. 
In 1920 E. de C. Clarke visited the Mt. Kenneth <listrict and colh'cted 
a suite of specimens of the metamor])hic roeks. Several of those hand speci- 
mens (1/2694, 1/2695) resemble very closely Talbot's specimen described 
above. Examination of thin sections failed to reveal the i>resence of any 
kyanite hoAvevei’, the indications being that these rocks have apjiarently 
failed to pass the chloi’ite stage of metamorphie doA^elopment (4, p 209). 
They consist essentially of (piartz, nuiseovite stained Avitli limonite, and some 
pale green chlorite. Of the accessories, rutile in bright yelloAv recrystallised 
prisms and dark detrital grains is most abundant. Others include detrital 
zircon and apatite. 
