118 
Geology and Physical Geography: 
nugget greatly exceeding 100 ozs. in weight having been found in 
any of the Upper Silurian gold-workings to the east of a line from 
Melbourne to Heathcote. Though this remark applies specially 
to alluvial workings, it may he also extended to quartz reefs, as 
larger masses of native gold have been found iu reefs traversing 
Lower Silurian rocks than have been discovered iu the Upper 
Silurian quartz-veins. 
The forms in which gold occurs in the reefs are various. It is 
sometimes evenly distributed through the stone, but is more 
frequently confined to some particular band, either on the foot or 
hanging wall, or, more rarely, in the central portion of the vein or 
lode. The auriferous portions of the stone in some places take 
the form of irregular disconnected patches, in others well-defined 
zones or “ shoots” of varying vertical width, which dip at different 
angles northward and southward in the direction of the strike of 
the reef. . The gold itself occurs in tolerably largo lumps inter- 
mixed with quartz, iu strings, ragged pieces, crystals, mossy 
aggregations lining cavities, and in fine specks. It is also found 
in mechanical combination with iron pyrites, a mineral almost 
universally present in greater or less quantity iu all quartz lodes, 
especially below water-level. 
Besides iron pyrites, copper and arsenical pyrites, galena, 
antimony, and zinc-blende, are frequent accompaniments of 
auriferous lodes, and in many mines one or other of these is 
regarded as an infallible indication of the proximity of gold- 
bearing stone. 
Investigations as to the primal origin of gold would probably 
prove as futile as inquiries into the origin of any othor metal or 
form of matter, but the question of how gold came to he associated 
with quartz in veins or lodes admits of at least a theoretical solu- 
tion, and the first stage of the inquiry relates to the origin and 
history of the quartz itself. 
Without entering into a description of the various different 
modes in which quartz lodes and veins occur, the broad fact can 
be stated that they occupy what were lines of fissure in the 
Silurian rocks. As to how those fissures were formed iu the 
rocks a general conjecture can be arrived at. It has been shown 
that the Silurian rocks — originally laid down horizontally — were 
crumpled, folded, and contorted so that their bands finally 
assumed positions approaching the vertical, and that, whatever 
may have been the cause, the forces operating were such that the 
longitudiual axes of the corrugations took iu Victoria, for the most 
part, an approximately meridional direction. Such movements 
could not take place without, in addition to the corrugation, con- 
siderable faulting, Assuring, and great local displacements, and the 
lines of fracture, naturally following those of least resistance, 
coincided in general direction with the strike of the schistose 
rock-bands. 
