18 The Extraction of Cold. 
pyrites in scattered crystals studding the rock. ~These 
crystals have been collected, and on assay gave from five to 
fifteen dwts. of gold per ton. This fact may throw some 
light on the cause of quartz veins being frequently pro- 
ductive above and poor below the water line; a circum- 
stance usually ascribed to the pyrites in the vein being 
undecomposed below the water. This is hardly sufficient 
to account for the sudden failure of the gold in depth 
in many cases, and it is possible that the existence of 
large quantities of undecomposed pyrites in the adjoin- 
ing slate beds may have an impoverishing effect, by hold- 
ing the gold and preventing its aggregation in the quartz 
veins. 
Hitherto I have only referred to the sulphides formed in 
the quartz or slate; but in the old auriferous drifts of Bal-_ 
larat the trunks of ancient trees are found imbedded in the 
gravel or drift, and on this old timber sulphides have fre- 
quently formed. A beautiful specimen of crystallized white 
iron pyrites deposited on a piece of wood taken from a drift 
immediately below the trap rock, gave by assay forty ounces 
of gold per ton. In another case where the old trunks were 
burst open, and only the sulphides formed in the heart of 
the tree retained, they were found to yield over thirty dwts. 
of gold per ton. Again, some of the fine dust obtained in 
washing off the gold at the Royal Saxon claim, Ballarat, 
yielded by assay over fifteen ozs.of gold per ton. When placed 
under the microscope this dust was found to be composed of 
minute crystals of pyrites, aggregated into round pellets, 
from one three-hundredth to one one-hundredth of an inch 
in diameter, the surface of each pellet being roughened by — 
the projecting angles of the crystals, and unwaterworn, in- 
dicating that the formation was subsequent to the deposit of 
the drift. These results show that the deposition of gold 
along with pyrites has been in operation at a comparatively 
recent date and is probably still going on. 
To enter into all the details of the researches made would 
extend this paper to too great a length, and it will be sut- 
ficient to state that careful trials, including assays of total 
contents, different modes of amalgamation “to ascertain the 
amount of free gold, and microscopic examinations, indicated 
that the bulk of the gold lost was enveloped in the pyrites, 
with rare exceptions, not more than one-fourth of the loss 
being free gold, and this was usually small flaky pieces 
floated off with the water. The proportion of this free gold 
