22 
RECORDS OF TITE AUSTRALIAN MUSEUM. 
much more opaque and vitreous-looking appearance than that 
seen in the other Mollusca, In one small guard in particular, 
now before me, remains of the radiating fibres and concentric 
layers of calcite are visible round the periphery, gradually fading 
off into a dark blue and purple vitreous-looking opal. 
Pre-eminent for its beauty is a bivalve, obligingly lent to the 
Geological Survey of N. S. Wales for examination by Mr. H. 
Newman, jeweller, of Melbourne. This is without exception one 
of the most beautiful conditions of fossilisation I ever beheld — 
perfectly clear of the matrix, with the valves in apposition, and 
save for a slight crushing about the centre of one of them, quite 
perfect, wholly converted into Precious Opal, and with a play of 
colour quite equal to the fragments in quartzite shortly to be 
referred to. The shell substance is almost glassy transparent. 
It is probably identical with the shell already referred to, with 
the translucent fractured edges, from the collection of Mr. G. de 
V. Gipps, also lent to the Geological Survey. 
Mr. J. E. Carne informs me that the Survey Collection con- 
tained, previous to the Garden Palace tire, an Ammonite, wholly 
converted into Precious Opal, six inches in diameter ! This came 
from White Cliffs, and was probably one of the first fossils ever 
obtained there. 
By no means the least interesting specimen found in this field, 
previous to Messrs. Tweedie and Wollaston’s reptile, is the half, 
split longitudinally, of a Sauropterygian vertebra, with the 
osseous matter converted in the first instance into the common 
white and opaque opal, and the canals and lacunse remaining 
open and filled with a little ferruginous powder. The roughened 
edges of the fractured surfaces are then tipped, and the cavities 
to some extent lined with Precious Opal. This is also from the 
cabinet of Mr. J. de V. Gipps. 
Some polished hand specimens of a highly fossiliferous chocolate- 
brown quartzite were presented by an unknown donor to the 
Geological Survey Collection, the whole of the organic remains 
being converted into Precious Opal, and the interstices between 
the component constituents of the rock likewise similarly filled 
as a secondary infiltration, probably replacing the calcite particles 
of the deposit. Beyond the fact that these specimens come from 
White Cliffs, I am not in possession of information as to the 
stratigraphical position of this quartzite, but possibly it may be 
derived from the water- worn vitreous boulders mentioned by Mr. 
Jaquet as occurring in the clay and conglomerate beds. The 
organic remains are those of Mollusca, with traces of Corals and 
stem-joints of Crinoids, showing such a marvellous kaleidoscopic 
play of colours that words are quite lacking to render the general 
appearance of the specimens appreciable. 
