276 DISCUSSION. 
Personally I have no doubt that the sapphires have come from 
basalt. The serious objection to this view is the occurrence of 
sapphire in the drifts under basalt. Sapphire is recorded as being 
associated with the diamond on the Cudgegong and at-Bingara,' 
and as the diamonds are derived from drifts that underlie basalt, 
the inference is that sapphire is also found in drifts under basalt. 
This is a difficulty that must be faced, and the explanation may 
lie in the fact that it is in redistributed drifts only the sapphire 
is found. At Tumberumba I never saw a trace of sapphire in the 
wash from the “deep ground” under basalt. ‘The sapphires I saw 
were all found in pleistocene drifts that must have received 
detrital matter from the degradation of basaltic hills.2, From the 
evidence before me I have no doubt as to the matrix of the 
sapphire, but it would be premature to say the question is settled 
absolutely. There is room for much more research, and another 
explanation may be forthcoming for the facts placed on record. 
Referring to the turquoise, I am not aware of any phosphate- 
bearing rocks near Bodalla, and it might be said that the rarity 
of phosphatic rocks is somewhat remarkable in this colony. Itis 
very satisfactory to hear that Professor David has detected radio- 
larian casts in “angel rock” from White Cliffs, the slides I 
handed him being slices of that rock, already described in the text. 
The views expressed may however be left on record for this reason: 
the opals found in New South Wales except at White Cliffs can 
be traced to igneous rocks the decomposition of whose felspars- 
supply the silica. After an examination of the White Cliff 
mines, I saw that there were no igneous rocks in the locality, 
and the opal was associated with the peculiar sedimentary len- 
ticular shaped rocks locally called angel-stone. This had many of 
the characters of an indurated diatomaceous earth, and agate 
1 Liversidge—Minerals of New South Wales, pp. ,. 237 and wal. 
2 Bernhard von Cotta states that sapphire occurs as an lg pro- 
duct in the basaltic lava of inde on the Rhine.—-Rocks C assified 
and Described, Revised Ed. p. 8. Specimens from this cat are not 
uncommon in Museums, 
