OCCURRENCE OF PRECIOUS STONES IN N.S.W. 255 
OPAL. 
The noble or fire opal, or the only variety that may be called a 
precious stone, is found in two localities only in New South Wales, 
namely, at the White Cliffs, about fifty miles from Wilcannia 
Station, and at Rocky Bridge Creek, near Trunkey. 
At Rocky Bridge Creek the opal fills vesicular cavities in a 
decomposed acidic or andesitic lava. The lava rests on auriferous 
gravels and sand§ of the usual Tertiary type. Some of the stones 
found here are of the finest possible quality. The larger stones. 
3 Section at Rocky Bridge Creek. a, andesitic trachyte with noble opal 
in vesicular cavities. b and ec, indurated sand and drift. d, Silurian 
slates. 
found are rather milky but show fine colours. The small gems 
lately got by Mr. S. Davis, of Carcoar, are not to be surpassed,— 
equal to the best Hungarian. As is well known the Wilcannia 
and Queensland opals are found encrusting or filling cracks, and 
the finest stones often want depth. The Rocky Bridge opals 
Occur in the matrix in rounded pea-shaped pieces. When a 
good stone of this kind is found, it can be cut to the best advantage. 
I do not think that the search for these opals ever has been re- 
munerative. There is a difficulty in getting out the gem,—at least 
the miner finds it difficult without a cutting wheel. At present 
Some men are at work, and as first-class stones have been found 
and the vesicular lava is extensively developed, more gems are 
certain to come to light. 
At the White Cliffs the opals occur in quite a different way. — 
They are not in any way connected, so far as I could see, with 
