GOLD NUGGETS FROM NEW GUINEA. 161 
GOLD NUGGETS FRoM NEW GUINEA SHOWING A 
CONCENTRIC STRUCTURE. 
By A. LIVERSIDGE, LL.D., F.R.S., Professor of Chemistry 
in the University of Sydney. 
[With Plates XII., XIII. ] 
[Read before the Royal Society of N. 8S. Wales, December 5, 1906. | 
THE two small nuggets referred to in this note were 
received from New Guinea; they show the usual water- 
worn appearance externally. The assays made at the Royal 
Mint, Sydney, gave for No. 1 nugget weighing °90 oz. gold 
8895, and silver 100 parts. No. 2 nugget weighing °86 oz. 
gave gold 8825 and silver 105 parts. 
When sliced, polished and etched with aqua regia, small 
enclosures of haematite and quartz, also cracks and cavities, 
become visible, but the usual macro-crystalline structure 
of gold is absent. Parts, however, near the edges possess 
a clearly marked concentric structure. 
As stated in the first paper upon this subject,’ this is the 
structure I then thought might be found; but out of the 
large number of nuggets examined for several years past, 
these two are the only ones in which | have been able to 
detect any indication of a concentric structure. Hence 
these nuggets are so far unique. 
It will be noticed that the section shows indentations 
which look like foldings or involutions. I do not think, 
however, that these are due to portions of the nuggets 
having been bent over, driven in, or welded on by impact; 
but it looks as if the gold, especially where it shows this 
1 See this Journal, Vol. xxvir., 1893, and Chemical News, 1894. 
K—Dec. 5, 1906. 
