12 
Keith R. Miles. 
slabs of roek which often stand up like (uiornious blunt spear heads. Both 
the Avestei'u and eastern slopes of the ridge ai'e ste(‘p to precipitous, and 
sti'ewn with these flat slabs and with smaller rock talus, and sprinkled with 
spaVse mulg'a scrub. 
On the western side of the hills this talus, together with red gravelly 
soil and milk white (piartz rubble, completely obs('ures the gcmlogy. To the 
east, though outcrojis are scarce', the country appears to consist principally 
of decomposed greenstone schists, probably schistose basic lava. On travers- 
ing the ridge southwards oiu‘ se^es that the ye'llowish (juartzose schist lenses 
out along till' strike, and without any visible uncemformity its phu-e becouu's 
taken by a banded ferruginous quartzite* bed. This relationship is shown in 
the gesiiogical skedch plan. (Fig 2.). Outcrops of this banded ferruginous 
quartzite* e)r jaspilite exle'iid southwarels in a series of low hills torming a 
curved line* linking up with the hills of the southern Gamed Jlunq). (See Fig. 
2.). Te) the imuu'diate* ne)rth ol' the northe*rn Camel Hump hills the cejiintry 
flattems out into a rubble-coveree! plain but traces of a baneled fe'cruginems 
■quartzite heel can be found extending for nearly a (piarter of a mile' te) the 
northwards. 
Vetrograpltjf. 
A close i7is])ection of hand specimens (L-d97.)^ of this yellowish-wliite 
rock taken freuu near the cairn at the* northe*r]i ('anud lUnnj) eliscloses the 
presence e)f a knotteel schiste>se strueTure. The* knots consist of kyanite in 
either rounded vathei* stumpy crystals ave'i'agiug about 2 mms. in eliameter 
and 2.5 mms. long, v)r longe'r Hat blaeleel crystals u]> te) (1.5 mms. in le*ngtb. 
Me)st e)f these crystals are* reuighly oriente'd so thal the*ir shorte'v axes lie* 
appre)ximate!y tunaual to the plant* e)i' schistosity. They are e'olourless and 
have* a lustre- ranging from dull vitreems to distine*tly pe'arly ui)e)n cleavagt* 
facers. The*se knots e)f kyanite are* st't in a "flowing’’ e)r folialt'd ai)hanitie' mat- 
rix of whitish, very lincly gi*annlate'd (piartz, usually tlt'cke'd with liny (lakes 
e)f se*ricite gi\ing a silky sh('e*n to surl"ae'e*s of the* ve)ck wiucli have bee*n bre)ke‘n 
parallel te) the* schistosity. This tpiartzose matrix is ln'i’e and the'i'e* staineel 
yelle>wish or pink by a little* intre)dne'eel limonito. 
If has a porpliyi'oblastic gneissic structure* — the pe)rphyroblasts of kyanite 
being arrange'el in laulely oidenteel bands of very irregular shaped evystals 
whose be)unelaries are fre(|uently eremulate'el and embaye'd, whilst the* teuiniua- 
tie>ns are gemwally resolved into a granular diablastic aggregate e)f' kyanite* 
and (piartz. 
Individual crystals of kyanite are occasionally curved and bent due to 
rotation during growth. In thin slice they are colourless and uou-pleoehroic 
and have characteristic high relief. Many elongated sections show a wedl 
defined cleavage (100) while sections cut paralled to this disedose an iuqierfect 
(010) cleavage. The cross parting (OOl) at a])proxiinately 85° to Hu* length 
of flu* crystals, i.e., the c-axis, is seldom well d(*velo])ed (See Fig. vlA.). 
End sej.ctious (cut approximately normal to the c-axis) disclose* the i>erfect 
(100) cleavage whilst the (010) is re[)re*sented by a strong e-ross parting at 
from 80°-85® to (100) (See* Fig. MB.) In such ■sections extinction is [)arall(d 
to (100) cleavage. 
* All numbers in parentheses represent either field or registered number.^ of specimens 
in the Geological Survey Kock Collection — except those preceded by the letter U, which 
helong to the General Collection of ihe Dept, of Geology. University of W.A, 
