1” 
ECONOMIC GEOLOGY 
washing in water. The conclusive evidence against the 
growth of nuggets in the gravels is their distribution. No 
nuggets are found in goldfields where the gold in the lodes 
is in minute particles; or they may be found, e.g. in the 
Rand in South Africa, only where coarse gold has been 
formed in secondary quartz-veins. In Ballarat East, as 
shown in Fig. 11, the nuggets were found along a line where 
nuggety patches occur in the lodes, 
These patches are exposed on the 
hillside ; pebbles washed down the 
slope, knocked out the brittle 
quartz and hammered the patch 
into a nugget. This origin is con- 
sistent with the investigations on 
nuggets of A. Liversidge (F.R. Soe. 
New South Wales, xxvii, 1893, p. 
343; xl, 1906, p. 161). 
The mining of Ballarat East was 
dependent on some clue to the 
arrangement of these nuggety 
patches. One having been found 
where a quartz-vein met g vertical 
brown line, this line was followed 
and led to other patches of gold, 
where it met a quartz-vein. The 
ine was therefore called the in- 
dicator. Several of these indica- 
‘ors have been found in the slates 
at Ballarat East, and have been 
traced for eight miles along the 
field. They vary from about one- 
sixteenth to a quarter of an inch 
in thickness; the main indicator 
sometimes divides into three layers which have a tota] thick- 
ness of half an inch. Their thickness and their dark colour, 
below the oxidized zone, is expressed by the names of the 
Pencil Mark and the Telegraph Line given to two of them, 
The microscopic structure of the indicators shows that most 
of them consist of bands of chlorite developed in the slate 
along planes of slipping (Fig. 12). The indicators in places 
occur along the cleavage planes, but often cross them. An