OCCURRENCE OF PRECIOUS STONES IN N.S.W. 253 
rate of two pennyweights to the ton. It has been mentioned 
that the turquoise has been found in concretionary masses. These 
balls, it may be noted, are oftentimes found completely imbedded 
in a very dark carbonaceous earth. The joints in which the tur- 
quoise occur are, as a rule, at right-angles or nearly at right-angles 
to the bedding-planes of the slate. 
When seen in situ a good deal of the turquoise appears of a good 
sky-blue. When mined and stored for a while the blue colour alters 
to a bluish-green, and often to a decided apple-green, showing little 
or no blue. The thickest seam found up to the present measures 
three-sixteenths of an inch in depth. Some of the best coloured 
stone is not more than one-sixteenth of an inch in thickness. 
Slabs of turquoise six inches long by three inches wide have been 
taken from the mine. 
With regard to the origin of the turquoise in this particular 
locality, there is very little evidence to base an opinion on. Prof. 
F. W. Clarke is of opinion that the turquoise of the Los Cerrillos 
mines is of local origin, and he emphasises the idea that it has 
resulted from the alteration of some other mineral, for instance 
from apatite. The existence of pyrite in the gold-bearing veins 
may have had something to do with initiating the process of alter 
ation, and the alumina of the turquoise was probably derived 
from decomposing felspar.! 
The presence of pyrites in the matrix of the New South Wales 
stone is a circumstance worth noting in this connection. It has 
been already stated that carbonaceous slate-rock is the matrix of 
some of the turquoise. In more instances than one I have noted 
at Bodalla concretionary turquoise, surrounded by a black powdery 
granular material not unlike a black oxide of manganese. But 
the borax bead shows no reaction for either iron or manganese. 
On heating, the carbonaceous nature of the material is at once 
made clear. If this carbon has had an organic origin a ices 
Senesis for this phosphate-bearing gem is apparent. 
' Gems and Precious Stones in United States, Canada and Mexico, by 
G. F. Kunz, p. 57. 
