The Geology of the Darling Scarp at Ridge Hill. 
J23 
be (M)ueeiitriUt'(l in the ll.Vl’iO mesh *^ra<le whereas in the feiTugiiious sand- 
stone they are most abundant in the bO-115 mesh j^rade (see text iig. 5). 
The minerals in'esent in the hea^ y fractions of all samples examined a|»pear, 
except for the abundance of epidote in the Crawley sand, to be. similar 
(Table \ ) even to the varietal features, indicating a common provenance 
lor all >am])l(*s. 
Notes on the Heavy Minerals. — The magnetic fraction consists partly 
ot strongly magnetic nKtfjti/'tite and partly of weakly magnetic ilmvnile. The 
dominant constituents of the noii-maguetic fractions of all samples are 
o|»a(jU(* mineraiS of which le}icoji'f^ne is predominant. The leucoxene is cloudy 
and slowly solid)le in hot sulphuric acid, the resulting solution yielding posi- 
tive tests for titanium. 
Tile noii-opaiiue minerals are: — 
Zi. cou. This is the predominant non-opaiiue mineral in all samples ex- 
amined. There are two di.stiuct types: (a) perfectly rounded, col-.uvies.s 
and (h) eiihedral prisms whicli may occasionally show signs of slight 
abrasii.n. The euhe<lral type includes colourless, colouiless with rodlike 
inclusions, deeji ])ur|)le, and |>ale yellowish zoned varieties, 'fhe purple 
zircons are particularly characteristic of the Kidge Hill ferruginous sand- 
•stone but some occur iu the yellow sand ot the Coastal I Main. All .samples 
contain both well rounded and eiihedral types of zircon. 
Kifanite is also iircseiit in all tin* samples examined. (lenerally colour- 
less but a few grains of blue kyaniti* were noted in the residue from the 
ferrugiiKius sandstone. The kyauite occurs in stout prisms ami tablets with 
well rounded teiininations. 
Slau-roliie in pleochroic yellow-ln'own granules of somewhat irregular 
shai>e never shows the high degree of rounding of the zircon and kyanite. 
It appears in all the sands (*xamini‘d hut seems to be confined to the (-oarser 
grades. 
lintUe in deep reddish brown prisms, oftmi well rounded was noted in 
all sam[)les. 
Kpldftit; was the most abundant non-opaque mineral in the (‘rawlev 
yellow sand. In tin' other samples it was vmw i‘an* except in the finest 
grade ( 250) of the yellow sand I'rom the south i-nd of the Ridge Hill 
area (sample C.) where it is very abundant in tiny angulai' grains. The 
epidote in the Crawley sand is in stout pri'^ms showing very little sign of 
abrasion. The abundance of epi<lote in tin* Crawley sand is Ihe main point 
(if difference between this sand and the Ridg(‘ Hill sands. 
generally well-rounded, is iiresent in all samples although 
nev('r alnindant. The most common variety is a strongly pleochroic clove 
bi’own tourmaline. A few greenisli brown tourmaline grains were noted in 
sainjile C. (Ridge Hill). 
SiUhuoifite Avas noted only in the Crawley sand and ferruginous sand- 
stone. It is in colourless fairly stout prisms. 
ITomblrude is of rare occurrence and confined lo tlie coarsest fractions 
examined. Roth brown-green and gre(*nish varieties Avere noted. 
PJponaste in Avell rounded, grreen, isotrojiic highly refracting grains is 
of rai'e occuri'cnce. 
