242 J. MILNE CURRAN. 
to the crossing-place to the Round Mount Diamond Mine, and 
also in the deep alluvial sinking at the Tingha Tin Mines. 
Professor David, in the report already referred to, makes mep- 
tion of a true emerald being discovered at Kiandra.! 
Probable origin of Emerald. 
Professor David writes, loc. cit., ‘There can be little doubt that 
the beryls and emeralds have been introduced into the joints or 
fissures in the claystone by solutions emanating from the under- 
lying intrusive granite.” Iam of opinion, however, that both 
claystone and granite received their gems from a common source. 
The topaz and fluorspar so prominently associated with emerald 
at Emmaville, are found even more abundantly in the granite than 
in the claystone. From a similarity in the occurrence and associ- 
ation of fluorspar and topaz in claystone as well as in granite, it 
seems to me that both granite and claystone were simultaneously 
invaded by the solutions carrying fluoride of silicon and fluoride 
of calcium, from which topaz and fluorspar crystallised. A com- 
parison of some of the best emeralds from Emmaville was made 
with some first-class emeralds from North America and Siberia. 
(a) Colowr:—The Australian stones were in no cases of as deep 
or rich a colour as the Siberian stones. 
(b) Lustre —It seemed to me that the Australian stone was — 
much superior to any others in lustre and life. This may 
be due in part to the cutting, the gems in my possession 
being cut by Mr. Murfin, lapidary, of Pitt-street, Sydney- 
(c) Hardness.—Our emeralds scratch quartz with the same 
facility as does the Siberian emerald, but both I found 
somewhat inferior in hardness to the white topaz associated 
with the emerald, and already referred to. 
(d) Specific Gravity.—The parcel of crystals photographed on 
Plate 15, fig. 1, have a specific gravity of 2°73. Some 
samples determined by Mr. Mingaye? gave a specific gravity 
7s caves! Report of the Department of Mines N.S. Wales, 1891, p- 231. 
2 Annual Report of the Department of Mines N. S. Wales, 1891, P- 233, 
