84 
The Queensland Naturalist May, 1938 
At first glance the path gives a false impression of 
uninteresting uniformity. This is due in part to the high 
percentage of dark pebbles and the consequent grey 
appearance of the whole, and in part to the fact that, 
before it was sold, the gravel was passed through screens 
to ensure a rough uniformity in size. 
But a closer examination showed a wide variety 
within this apparent sameness, and I was able to recog- 
nise many old friends among the pebbles, reminders of 
numerous geological excursions to different parts of 
South-Eastern Queensland. 
Perhaps the most striking, although far from the 
commonest pebbles, are the jaspers. In contrast to most 
of their fellows, these are red or reddish brown in colour. 
Nor are they nearly so well rounded and polished as the 
other pebDies, and it is these exceptional features in 
colour and form that attract the eye. 
Some of these jaspers, when examined with the lens, 
show numerous minute spherical spots. Each of these 
lepiesents the skeleton of a radiolanan, and they are so 
pientuul m some cases that more than a million are con- 
tained in a cuoie inch of the jasper. And yet so small 
are these primitive organisms that they are by no means 
crowded. 
Far more numerous, if individually less interesting 
than the jaspers, are the cherts. These are for the most 
part dark grey or black in colour, and give to the gravel 
its characteristic grey colour. They are almost without 
exception well rounded, and often are highly polished. 
Forming an interesting contrast with the black 
cherts, although less abundant, are cream quartzites. 
These, together with colourless and pink pebbles of 
quartz, form the majority of the lighter coloured con- 
stituents. 
Banded quartzites are also found, but these are 
usually flatter than the other pebbles and less rounded 
than most. 
One of the commonest groups is made up of ande- 
sites. These, although they vary very considerably in 
colour and texture, have so many other characteristics 
in common that they fall naturally into an easily recog- 
nised group. Perhaps the most striking feature uniting 
all these andesites is their porphyritic character due to 
the presence of phenocrysts of plagioclase that have 
weathered into conspicuous white crystals. Again, the 
andesites, although rounded like the other pebbles, differ 
from them in lacking their smooth polish and having 
