\ 
OCCURRENCE OF PRECIOUS STONES IN N.S.W. 277 
a diatom ooze as the source of the silica. The probability is that 
it was a radiolarian deposit. But this fact stands out, that at 
White Cliffs, shells, belemnites, etc., are converted into noble opal 
by a silica derived from organic sources, and at Rocky Bridge 
Creek a noble opal is found, filling vesicular cavities in an andesitic 
trachyte, and its silica is derived from decomposing felspars. 
The points raised by Professor David were most important, but 
the complimentary tone of his remarks could not make the author 
forget that there is necessarily much debatable matter in a paper 
covering so much ground. 
Mr. Henry Smith’s criticism contains much compressed into a 
small space ; it will be better to take his statements seriatim, so 
as to prevent any confusion of ideas. Mr. Smith’s remarks are 
also so incisive, although to a less extent than in their original 
form, that anything short of direct reply would hardly meet the case. 
Mr. Smith—* Mr. Stephen’s collection of gem stones is now the 
property of the Government of New South Wales, having passed 
into the possession of the Technological Museum.” 
Reply—In this statement Mr. Smith is in error, as Mr. 
Stephen’s collection—probably the finest made in Australia—was 
broken up and sold. Dr. Bleasdale of Melbourne purchased the 
best: rubies and sapphires. Part of the original collection is now 
in my cabinets, other parts of it were sent to London. There is 
it is true, a small collection of gems, made by Mr. Milner Stephen 
in the Museum of the Technical College. They were sent there 
from my laboratory. This collection had passed from Mr. Stephen’s 
Possession many years ago, and was in the hands of dealers for 
Some time, finding its way finally to the Australian Joint Stock 
Bank, from whence I got it in a state of complete disorder. The 
replacing of many of the labels and the disposition of the speci- 
mens, was due to the good offices of my laboratory attendant—an — 
enterprising youth whose ambition seems to have been, to find a 
Specimen for every label! 
Mr. Smith—« Tn it (the collection) was a cut stone from this 
locality, near Mudgee, said etc.” 
