7 
“ The colours visible by reflected light are principally blue, red, green, 
and yellow, with their various shades and combinations, not the least pleasing 
being an ever- varying degree of red and blue-tinted purple. 
“ When tlie fossils are in the form of kaolin casts, specific identification, 
with a very few exceptions, is almost unattainable. Those in which opalisation, 
however, has taken place, arc always determinable, more or less, and the 
substitution of the original carbonate of lime has been very thoroughly 
carried out. Fragments of these opalised remains, chiefly shells, are freely 
scattered throughout some hand specimens of the opaline kaolinised con- 
glomerate, from the bed B of Mr. Jaquet’s section. The kaolin casts are 
either white or tinged with iron-oxide, arising from the highly ferruginous 
clays that Mr. Jaqiiet says the kaolin passes into. 
“ The opalised fossils comprise Crinoid remains, the shells of Pelecypoda 
and Gasteropoda, portions of Belemnite guards, Sauropterygian bones. The 
preservation of some of these fossils is excellent, although all are not alike in 
this respect, and the extent to which the opalisation has at times l)een carried 
is remarkable. 
“ In some Pelecypoda, the external growth laminm, and intermediate 
sculpture striae are fully preserved, whilst the shell substance is completely 
changed, and by transmitted light the valves of many are almost transparent. 
On the fractured edges of one of these bivalves the glassy opal is quite trans- 
lucent by reflected light. "When such valves are met with in apposition, the 
interiors are often found to be filled witli soft kaolin, and no better examples 
of the complete change that has taken place can be examined. 
“ The replacement of the fibrous calcite of the Belemnite guard, when 
viewed in cross-section, presents a far less translucent, and much more opaque 
and vitreous-looking appearance than that seen in tlie 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 liivalve, obligingly lent to the Geolo- 
gical Survey of N. S. AVales for examination by Mr. II. Newman, jeweller, ot 
Melbourne. This is without exception one of the most beautifid 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 
