XXVIII. ABSTRACT OF PROCEEDINGS. 
1. Mr. H.C. ANDREWS exhibited numerous polished slices 
of ore and country rock from the Great Cobar Copper and 
the Mount Boppy Gold Mines, also specimens of ore from 
the Budgerygar and Tottenham Copper Mines. Large 
hand specimens of slate and sandstone from the Mount 
Boppy Gold Mine were also shown. The exhibits were 
selected from a collection of specimens obtained during the 
geological survey of the Cobar and Canbelego Mining Fields, 
and they illustrate in a striking manner, the great alter- 
ation which the rocks of the districts under consideration 
have undergone. The ores exhibited from the Great Cobar 
Copper Mine are massive copper pyrites, magnetic pyrites, 
magnetite, galena, zinc-blende, and iron silicate, in intimate 
association and which occur as lenses of enormous size in 
slate within a wide zone of faulting or crushing. The 
great lenses under consideration represent the replacement 
of slate by ore solutions. In other ore specimens exhibited 
from the siliceous deposits of Cobar, magnetite, magnetic 
pyrites, and iron silicate are almost completely absent. 
These siliceous ores, however, represent replacement by 
silica, iron sulphide and gold, solutions within long zones 
of faulting. The Budgerygar and Tottenham copper ores 
exhibited, illustrate the action of selective replacement in 
sandstone and slate which have been highly folded and 
puckered. Thin and puckered layers have been replaced 
by sulphides although intermediate layers exhibit slight 
replacement only, in the nature of iron pyrites as crystals 
scattered throughout such layers. Types of structure 
strikingly suggestive of miniature ‘saddles’ and ‘inverted 
saddles’ are common in the Tottenham mines. ‘The 
specimens exhibited of the country rock from the Mount 
Boppy Gold Mine consist of crossbedded sandstone and slate 
which have been intensely puckered. Undera strong lens 
these puckered layers show faulting of overthrust nature. 
