ORES OF GOLD 
30 
and as the deeper ore is poorer, in 1923 only 7 lode mines were 
at work, 
The Ballarat Goldfield is another historic field. The 
discovery of its rich alluvial deposits in 1851 established the 
mining fortune of Australia and led to the great influx of 
Population. The field consists of Lower Palzozoic slates 
and quartzites, with felsite dykes derived from granite that 
outcrops 2 miles to the east. At Ballarat West the lodes are 
continuous quartz-veins, that vary in width from 2-10 feet, 
and expand into replacement bodies 100 feet thick. The 
gold occurs in irregular shoots which have been worked to 
the depth of 1300 feet; the gold yield decreased downwards 
though in places the copper, galena, and blende increased. 
In the goldfield of Ballarat East the quartz-veins form an 
irregular branching and intersecting network. Most of the 
quartz is barren, but along the veins are rich irregularly 
branching patches of gold. These “ nuggety patches” have 
given rise to the nuggets (a term probably based on ingot) 
which were found in the local gravels. Nuggets are usually 
rounded masses of gold, some of which are free of quartz 
and have g concentric structure. The Welcome Stranger 
Nugget, found at Moliagul in N.W. Victoria, contained 
£10,000 worth of gold. The belief is persistent among 
TURers that the nuggets grow in the gravels, as none have 
been found in lodes, and as the gold in nuggets is ** finer’ 
(Le. purer) than that in the adjacent lodes. Support to 
this view was given by an experiment that suggested that 
gold dissolved in water circulating through the deposits 
would be precipitated on free gold, which would grow into 
nuggets, as flints grow in chalk. The existence of gold in 
the water of alluvial deposits in British Guiana hasbeen proved 
by Sir J. B, Harrison. It has also been found in the rotting 
vegetation of many placers; but this gold has probably 
been carried there mechanically, just asin the * moss-mining 
of California the gold in the ash of moss collected from the 
rivers was probably filtered from the water and not precipi- 
tated from it. Aliuvial gold is finer than it was when in a 
lode, as silver, being more soluble, is removed by prolonged 
Lo. . ory, 
A Baragwanath, Mem. G.S. Victoria, xiv, 1923; J. W. Gregory 
ibid, iv, 1907.