46 
fills joints and cracks in the black carbonaceous beds. The concretions con¬ 
sist of 28'2 per cent, of hydrated oxide of iron (principally ferric iron), 
alumina and a large proportion of fine silica. As a pigment this material, 
when burnt, possesses some good qualities. The grey beds in which the con¬ 
cretions occur consist of fine soft sandstone with a little ferruginous matter. 
The black carbonaceous beds are the most interesting. An analysis of 
an average sample from the cliff on the east side of the river was made in the 
Geological Survey Laboratory and gave the following results : — ■ 
per cent. 
Moisture .. .. .. .. 17‘34 
Carbonaceous matter .. ■ .. .. 9*28 
Ash .. .. . . . . . . 73*38 
100*00 
The ash, on partial analysis, gave :— 
per cent. 
Silica .. . . . . .. .. 81*8 
Alumina .. . . . . 8*9 
t 
Iron .. .. . . .. . . 4*6 
Calcium .. .. . . .. Nil 
Magnesia .. .. .. .. 1*5 
96*8 
In the bed of volcanic ash iron pyrites is plentifully present. The fine 
siliceous sand on the beach appears to be directly derived from the wearing 
down of the cliffs. 
Mr. Deans, of Geelong, has persistently bored in this neighbourhood for 
mineral oil, but hitherto with no success. At the surface there is no evidence 
that it exists, but great stress is laid on the fact that gas at two of the bores 
ejected black mud churned up in boring. This in itself is no evidence that 
such oil exists. What may exist at a greater depth it is impossible to say. 
[23.8.11.] 
MAGNESITE AND CLAY AT SPRING CREEK, EOWSLEY, NEAR 
BACCHUS MARSH. 
By D. J. Mahony, M.Sc., F.G.S., Petrologist. 
The magnesite deposit in this locality is situated in the valley of Spring 
Creek, on Mr. D. O’Keefe’s farm, section 5g, parish of Bungeeltap, about 6 
miles west of Rowsley railway station, and 12 miles from Bacchus Marsh. 
The valley is steep sided, about 200 feet deep, and the rocks exposed are basalt, 
about 60 to 80 feet thick, resting on a series of Tertiary clays. The magnesite 
is found near the creek-level where it occurs in nodules ranging up to 30 or 
40 lb. in weight and irregular in shape. It is also found in a shot-like form, 
and has a fairly soft clay-like material; the last is exceedingly difficult to 
distinguish from the white clays which are abundant in the vicinity. The 
magnesite nodules are fairly abundant in the creek bed, and one small hole that 
has been sunk exposes hard nodules embedded in the softer form of the same 
material, but until some more work is done it is impossible to judge the extent 
of the deposit. It might be tested by sinking holes wherever there are 
