In
countries blessed with abundant rainfall the nuggets can be separated from
the dirt by a comparatively simple arrangement of sluices and cradles. In
the drought-stricken west of Australia other means must be adopted, which
I will endeavour to describe.
Having picked and dug out a certain amount of the alluvial ground which,
it is hoped, contains nuggets of various sizes, the digger then breaks up
any lumps of clay or earth by means of a heavy billet of wood, or like
implement, and this prepared dirt, as it is called, he treats in one of
the following ways: -
1. BY MEANS OF TWO IRON DISHES, in diameter 15 to 18 inches, and in depth
4 to 5 inches.
One dish is placed empty on the ground, the other, filled with the
prepared dirt, is held up at arm's length above the head, with the mouth
of the dish turned to the wind; the earth is then allowed to fall
gradually into the dish beneath, all light particles and dust being blown
away by the wind. Exchange of dishes having been made, the same process is
repeated again and again. When there is only a small amount of dust left,
the full dish is held in both hands, and given a circular movement, which
causes the larger stones or pebbles to come to the surface; these are
cleared away with the left hand, and a sharp look out is kept for nuggets
or quartz specimens. This is repeated until nothing is left in the dish
but a small quantity of dust, ironstone-gravel, and possibly fine gold, or
small nuggets. The dish is then held up at an angle, and shaken from side
to side until a compact little heap remains, to the bottom of which the
gold will have sunk. The next and final operation is to hold the dish up
to the mouth nearly horizontally, and blow the little heap across the
dish. Any fine gold will then be seen lying on the bottom just under the
nose of the operator.
Given a good hot summer's day, flies as numerous as the supply of water is
scanty, clouds of dust, little or no breeze, and the same quantity of
gold, and a few score of men working within an area of nine or ten acres,
one is sometimes tempted to think that gold may be bought too dear. But
the very lowest depths of despair, cannot compare with the heights of
satisfaction, attained after a successful day's "dry-blowing."
2. BY MEANS OF TWO DISHES, AND A TRIPOD STAND AND PULLEY.
A tripod, twelve or fifteen feet high, is set up over a hard and smooth
piece of ground. By a rope and pulley the full dish is hauled up as far as
required; the rope is then made fast and a string, fixed to the edge of
the dish, is pulled, and the dish tipped up allowing the dirt to fall on
to the prepared surface below, where it is swept up and treated as in the
first method described. With a fair breeze this is a very effectual way of
getting rid of the fine dirt.
3 BY MEANS OF A SIEVE.
This method is only suitable when the soil is wet and sticky, or where the
nuggets are fairly large and not too rare.
On the first rush to Kurnalpi, where more alluvial gold was found in a
short time than on any other field, sieves were almost the only implements
used.
A sieve is very useful for prospecting the surface soil, being more
portable and more rapidly worked than the dishes.
A combination of these three methods is found in the DRY BLOWING MACHINE.
It has always been a hotly debated question, whether what is known as the
"Cement" comes under the heading of "reefs" or "alluvial." This cement is
composed of angular quartz-fragments, broken from the reefs or veins,
and fragments of diorite and hornblende schists, cemented together by
lime; it is very hard and solid and, in places, continues to a depth of
over twenty feet. The gold is extracted from these depths by crushing and
dry-blowing. I have mentioned this peculiar composition last, as I am not
at all clear to which class of formation it belongs.
At first this cement, which the shallow alluvial ground overlies, was
supposed to be "bottom," that is to say, that there was considered no
likelihood of gold being found at a greater depth. Later developments,
however, have proved this theory to be wrong, and with regard to this I
cannot do better than quote extracts from a report made by
Mr. E. P. Pittman, Government Geologist of New South Wales, in which
he says: -
"He had considered the question of deep-leads of alluvial, and after
visiting Coolgardie, Kalgoorlie, and Kanowna, he thought it probable that
there would shortly be a large output of alluvial gold from this source.
In Coolgardie the dry-blowing had been confined to a very shallow depth,
and yet close to Coolgardie - in Rollo's Bore - there was evidence of the
existence of a very deep valley. He produced a specimen, taken by him
from an alluvial working near the Boulder Mine, showing what the
dry-blowers had all through regarded as the natural floor of the alluvial.
Below this floor they had never penetrated until the enterprising
prospector at Kanowna recently did so, and followed the lead down to
fifty feet.
" . . . He was satisfied that the alluvial went down to a depth at
Kalgoorlie just as it did at Kanowna. All the conditions were favourable
to deep-leads of alluvial.
" . . . Rollo's Bore at Coolgardie had proved the existence of alluvial
gold at great depths.
" . . . So far the alluvial men had been working on a false bottom."
At the time of writing, some two thousand men have found profitable
employment in working this newly discovered deposit; and doubtless
conditions similar to those found at Coolgardie, Kalgoorlie, and Kanowna,
will be proved to hold on other alluvial fields, formerly supposed to be
worked out.
