The Geology of the Darling Scarp at Ridge Hill. 
125 
Garnet is also very rarOj in j’oinuled ('olourless to pale pink grains. 
Monazite in peiTeetly rounded, pale yellow grains is most abundant in 
the ferruginous sandstone, l)ut even there is ('■omi)aratively rare. 
Shape analyses indieate that all samples show similar eharaeteristics. 
As indicated in figure six the average sphericity is constant in all grades 
for each of the samples examined and the avei'age round tiess decreases Avith 
diminishing grain size in all sanqjles. Figure six shows the distribution 
of sphericity and voinulness in the whole sam[)le anti it will be noted that 
there is a greater spread in the degree of rounding of the grains of the 
ferruginous sandstone than in the yellow sands — this is the only a).'preciable 
ditference in the shape analyses. The similarity in the various sam):)les in- 
dicates that so fai‘ as the factors affecting shape are concerned they all had 
a common type of origin. 
Examination of the surface textures of the grains in these different 
samples revealed the following: — 
Sample 
and 
Grade. 
.Surface Texture 
60-115 mesh. 
il-l mm.) 
32-60 mesh. 
(|-i mm.) 
16-32 mesh. 
(1-1 mm.) 
A. 
22804 
Yellow 
sand, 
Crawley. 
5% of grains well 
rounded, smooth, high 
])o ish. hut a few grains 
are frosted. 05% 
roiarh, vitreous frao 
1 11 r e surfaces. 
Heavies ” show 
marked rounding and 
high ])olisb 
40^0 smooth, frosted 
with later superim- 
posed ])olish. 60% 
rough, vitreous fra- 
ture surfaces 
90% smooth, frosted 
crescentic percussion 
marks common. 10% 
rough, vitrcious frac- 
ture- sujfacos 
B. 
21304 
Yellow 
sand. 
Ridge 
Hill. 
5% well rminded, 
smooth, polished, few 
grains frosted, some 
with per<’iission mark.s. 
95% rough vitreous 
fracture surfaces. 
“ Heavies ’ ’ show 
marked rounding and 
liigh ])olisIi 
Higher proportion of 
smooth grains than in 
60-1 15 grade. Smooth 
grains frosted but 
some are polished. 
Rough grains slightly 
frosteil 
80% smooth, all frosted 
with slight superim- 
posed polish. Per- 
cussion marks com- 
mon. -0% rough, 
polished to slightly 
frosted 
C. 
22802 
Yellow 
sand, 
Loc. 1298, 
Ridee 
Hill. 
5%-10% well rounded, 
smooth, polished to 
slightly frosted. 90%- 
95% slightly rounded, 
rough, polished or 
vitreous fracture sur- 
faces 
Similar to 60-1 15 grade 
but much higher pro- 
portion of rounded 
grains with slightly 
higher degree of frost- 
ing. (’rcscentie per- 
cussion marks on 
many rounded grains 
Similar to 32-60 but 
degree of frosting on 
rounded grains is 
higher. A polish seems 
to be superimposed on 
the frosting. Percus- 
sion marks common on 
rouiifled grains 
1). 
22798 
Insoluble 
residue 
from fer- 
ruginous 
sandstone 
Ridge Hill 
5% roimded. smooth, 
polished, often pitted 
but not frosteil. 95% 
rough. ])olishcd or 
vitreous fracture sur- 
faces. ( 'onlains small 
amount of tulau-osti 
allophanoid 
50% rounded, smooth, 
polished, often ]>ittcd, 
a few grains frosted, 
some with crescentic 
])erciission marks. 
50% rough witl) 
])()lished or vitreous 
fracture surfaces 
90% rounded, smooth, 
dull to polished with 
minute pitting and 
crescentic ])erciission 
marks. 10% rough 
with polished or vitre- 
ous fracture surfaces 
