322 
FURTHER NOTES ON AUSTRALITES. 
By E. J. Dunn , F.G.S., late Director , Geological Survey. 
Since Bulletin 27 (Australites) was published, additional material 
bearing on the subject has been secured, and is embodied in the following 
notes : — 
Black Basalt. 
* In Selwyn’sf Quarter-Sheet 9 S'.E., showing the country around Kyneton, 
this note is inserted over an area lying between the Coliban and Little 
Coliban Rivers, and about 2% miles S.W. from Kyneton township—“ A 
black, jetty, very dense, slaggy-looking basalt is found all over the ground 
without appearing anywhere in place.” 
This rock extends for a length of about half a mile, and is found in 
the northern portion of allotment 308 and in the N.E. corner of allotment 
307, parish of Lauriston. It occurs as loose, very irregular fragments and 
blocks, ranging to over 50 lb. in weight, scattered over the northern 
portion of the area, evidently the remains of an irregular sheet, all of which 
has decomposed except the loose pieces. Very red soil has resulted in 
places from the decomposition of this rock. In the southern portion of 
the area this black basalt, which resembles lydianite in appearance, is met 
with in place, as an irregular sheet between flows of grey vesicular basalt. 
Nowhere was it observed to exceed a foot in thickness. 
This basalt is an acidic rock, as shown by an analysis published in 
Selwyn’s catalogue of 1868, page 23. The composition is as under :— 
Analysis by J. Cosmo Newbery. 
Per cent. 
Silica ... ... ... ... ... 61.96 
Alumina ... ... ... ... 17.23 
Manganese ... ... ... ... 0.96 
Iron ... ... ... ... ... 10.43 
Lime ... ... ... ... ... 5.36 
Magnesia ... ... ... ... 3*24 
Potash | 
rt j f • • • • • • • • • • • • 2.IO 
Soda ) 
Titanic acid ... • •• ••• 0.60 
Water ... ... ••• ••• 0.07 
or .95 
Waterworn pebbles of this acidic basalt are abundant along the course 
of the Coliban River, from the Upper Coliban Reservoir to Tara dale, and 
still further down stream in the Recent alluvial gravel, but are not present 
in the auriferous alluvial leads of Tertiary age. Pebbles of this basalt are 
also’ found in the Coliban River for 2 miles above the reservoir, but 
sparselv distributed. None were observed so high up as Trentham. 
The rugged, irregular, and extremely rough forms that the remnants of 
this rock assume as a result of decomposition are remarkable. They some¬ 
what resemble the forms met with in obsidian on the Great Barrier Island, 
New Zealand. 
Owing to the hardness and sub-conchoidal fracture of this basalt, it 
was peculiarly suitable for forming the weapons and implements required 
by the aboriginals, and it was largely used by them. Chips of this 
material are found for long distances around where this rock crops out. 
