72 A. LIVERSIDGE. 
sulphur dioxide and air. The water vapour was probably derived 
from the hydrous oxide of iron and argillaceous matter enclosed 
in the nuggets, and the sulphur dioxide from pyrites or other 
su)phur containing minerals. 
The nuggets examined came from various parts of Australia 
and differed considerably in purity; the purer ones usually pre- 
sented a much better marked crystalline structure—this is well 
shown in the specimens from West Australia. Plate 1 reproduces 
a photograph of a nugget from Coolgardie, W.A., enlarged two 
diameters so as to render the external details clearer. The some- 
what rounded and worn points show traces of crystalline form, 
probably that of the octohedron and its derivatives. On the 
whole the nuggets from West Australia which I have seen did 
not possess such a worn and rounded appearance as that usually 
presented by large nuggets from other localities, and I am inclined 
to think that they are less water worn on account of the greater 
dryness of that region. The weight of this nugget was 9°94 oz. 
Troy, and the Mint assay was gold -8900, silver -105. 
The assays given in this paper are those of the average of the 
parcel of gold from which the nugget was selected, the assays of 
the individual nuggets and of portions of the nuggets have yet to 
be made. It is intended to cut out crystals from the sections and 
examine them separately to see if there is any difference in their 
composition. Some of the crystals are much more deeply etched 
than others, that this is the case can be seen from the photographs, 
which by no means give all the details. 
The external depressions of this and other West Australian 
nuggets contained a little clay, which under the microscope 
showed the presence of a few spangles of gold and some small 
particles of quartz with sharp edges and conchoidal fractures. 
One small fragment of galena was also detected. Internally the 
nugget was practically free from foreign matter. Plate 2 is from 
a photograph of an etched section of the nugget taken very near 
the median plane. Plate 3 shows the other side of the same 
section but more deeply etched. A few minute cavities can be 
