A VISIT TO THE SOUTHERN GOLD FIELDS.
QUARTZ CRUSHING AT ADELONG – ITS CHEMICAL DIFFICULTIES.
FROM OUR SPECIAL REPORTER>
No. 5.
Having, in my last two letters, described the process of raising the auriferous quartz from the great reef, we
will now follow it to the crushing mills; these are situated, with one exception, on the margin of the Adelong
Creek, following the windings of the stream round the base of the mountain to the point where it enters the
rocky gorge through which it precipitates itself to the lower levels in its progress to the Murrumbidgee.
There are at present five mills worked by steam, and four driven by water power; with one powerful steam
machine and three additional water mills in various stages of progress. Of those now in operation, the
highest on the creek is the Leviathan, of twelve-horse power, the property of Davidson and Company,
working two batteries of four stampers each. The machine is fed from a hopper in the rear, and each
stamper falls with a weight of 350 lbs. from a height of twelve inches, making fifty-two descents per minute.
The stone, when reduced to sand, is carried by a regulated stream, passing through the stamping-box
along a trough into the Chilian basin; here it comes in contact with quicksilver, and is operated upon by two
revolving rollers, each weighing two and a half tons, which reduces the auriferous sands still finer, and by
pressure and trituration, facilitates the amalgamation of the metals. The surplus water carries with it the
lighter particles of sand and other minerals, also a portion of the mercury and gold, which, having formed
new combinations with the sulphurets and arsenites, is either held in suspension or driven to the surface by
the concentric motion of the stream passing through the basin, and escapes through a slot in the
side, being received in a trough which conducts from a shotting table. Here they are again made to
pass over a quantity of quicksilver kept in a state of constant agitation, and are received into a tub also
containing quicksilver, in which a rotary motion is kept up by a band in connection with the engine.
From this vessel the water escapes over the rim, conveying with it the refuse and debris kept in suspension
by the rotary action within.
The operation of crushing is now carried to great perfection, the tailings from most of the mills at work being
nearly as fine as flour; but the process of amalgamation has not been so successful. There is no certainty
that much of the gold is not carried away, and there is a certainty that a considerable loss of quicksilver is
sustained, sometimes amounting to more in value than the sum charged for crushing, and always
sufficiently important to cause a serious reduction in the profits of the mill owner. This loss of quicksilver
occurs in two ways. The first results from the grinding action of the Chilian rollers; the second and greatest
is by the affinity of some of the constituents of the coarse coppered mundic for mercury. Where the former
is mixed with black masses it is most destructive. When stone is passing through the mill containing a large
proportion of this mineral compound, the greatest loss occurs. A leaden greasy scum is observed to rise
to the surface of the water in the basin, on which minute globules of quicksilver are seen floating, and, on
drawing off the fluid for the purpose of cleansing -out, a black unctious paste is discovered on the mercury,
and air or gaseous bubbles are seen rising through it. In one instance, the amalgam adhered to and
clogged the rollers, and it was found necessary to cut it off with a cold chisel. In fact, so great was
the excitement on the part of the miners, that they were with difficulty restrained from destroying the
mill. Although good mechanics and engineers are numerous on the gold-field, there is not one person who
has the least pretensions to chemical science.
The result of this loss of quicksilver is, that mining operations are retarded in the district, as the cost
of crushing and amalgamating is of necessity so high, that hundreds of tons of auriferous quartz are
thrown aside that would be sent to the mills if the rate was lower. Many reefs, also, have been abandoned
that would yield from one to two ounces per ton, as, after paying the crushers at the present rate, a
sufficient balance would not remain to cover the cost of cartage and raising. The miners do not hesitate to
say that if the Adelong had the good fortune to be situated to the south of the Murray, the Victoria
Government would have directed their attention to the subject long since. It is probable that Professor
Faraday, or some of the most celebrated chemists of Europe, would suggest a simple remedy if the matter
was laid before them by the colonial authorities. Mercury has an affinity for so many minerals, and enters
with them into so many combinations, that none but those capable of analysing the various products of the
auriferous quartz in combination with that metal will be able to direct our miners how to neutralize an agent
that has so entirely baffled their exertions, of which they have had no previous experience, and that has
hitherto proved so destructive to their interests.
After the water is drawn off, the amalgam is collected from the Chilian basin, the shaking tables, and the
tub, and poured out; the loose quicksilver is pressed through a double fold of unbleached calico, and the
remainder placed in a retort-a tube from which is inserted in a tub full of water. Upon the application of heat
to the retort the mercury sublimates, and is found pure in the tub, while the residuum is gold, with its alloy
of copper or silver, as the case may be, and the relative proportion of either
in the mass determines its value.
The Leviathan crushes from seven to nine tons, according to the stone operated upon, every twenty
four hours.
The next mill is the Old Pioneer, twelve-horse power, steam, now driving one battery of four stampers-can
work eight; she crushes from three to five tons daily. Here vis a vis on the other side of the
stream is the Wheel of Industry, water power, driving eight stampers and a Bredon basin; her task is three
to four tons every twenty-four hours. Recrossing the creek, you arrive at The Enterprise, sixteen-horse
power, steam, now working three batteries of four stampers each; she is prepared for a fourth battery,
making sixteen stamps in all. The weight of each stamper is 500 lbs., and it makes fifty-eight descents per
minute; the battery thus striking 55,680 blows per hour, and crushing about twenty-four tons daily. This
finished piece of mechanism has been but just completed, and may be hardly said to have commenced
operations, as her only performance hitherto has been with the object of testing and regulating the
machinery. The workmanship would pass muster in the best establishments of Birmingham or Manchester,
and does credit to our young country. The proprietors have discarded the Chilian basin and rollers, placing
their chief dependence upon the amalgamating facilities afforded by the shaking tables and tubs. These
latter consist of three vertical cylinders placed one within the other; two of these revolve with great speed.
The stream is received in the central tube, from which it escapes to the second compartment, through an
open space left at the bottom for that purpose; from the second it over- flows into the third, and from the
third it is allowed to run into the creek, flowing over the rim. The contents are kept in motion by agitators
driven by bands and pulleys in connection with the main power.
We now proceed to the Reefer, one of the most perfect crushing machines yet erected on the Adelong; it is
one of King and Howland's patent, and was manufactured by Messrs. P. N. Russell and Co., of Sydney. In
California it is said to supersede all others, and may be described as follows :
The bed plate of the battery pan is three-and-a half inches thick, and seven feet in diameter; the mortar five
feet in diameter, eight inches in depth, and of a circular form, having on the upper edge a drip flange seven
inches wide. Recesses, half an inch in depth, are sunk in the bed plate for receiving dies, on which the
stampers drop, thus saving the wear of the plate; the dies are three inches thick, and with constant use will
last three months. The frame consists of six cast-iron pillows, cast hollow, through which wrought iron rods
extend from below the flange of the mortar through the top plate of the machine; these rods are fastened
under the mortar with key bolts, and at the upper end with screws and nuts. Two feet ten inches from the
bottom rests the feeding plate, fastened with bolts and screws, and one foot eight inches above this is
another plate, fastened in like manner; and two feet ten inches higher is the top plate pillows, resting on the
fastened by the rods and nuts previously described: there are holes through all the plates for the iron stems
of the stampers. In the centre of the mortar is a column four feet six inches in height, two feet three inches
at the base, and tapering to one foot at the top, on which a cast iron step with steel centre is fitted, in which
the cam shaft revolves. The cam wheel is two feet two inches in diameter, with three cams, or
inclined planes, capped with steel on the upper edge, each having a drop of ten inches, each cam is
beviled so as to fit the toppit by which the stamps in ascending receive a rotary motion, thereby keeping the
face of the stamper perfectly flat; the stems are made of wrought iron turned smooth, and two feet six
inches from the top a screw is cut, on which a cast iron toppit, with lower face beviled to fit the cam is fitted;
as the stamps, shoes, and dies wear the toppit can be raised or lowered so as to regulate the fall of the
stampers, the cam shaft passing through a collar in the top plate carries a three feet bevil wheel made to
work in a ten-inch pinion, the latter being fixed on a horizontal shaft having a fixed pully by which the whole
is set in motion; a loose pulley is also fitted on to this shaft, on to which the belt that connects the machine
with the main driving power is drawn by a lever, thus stopping the motion of the stampers in an instant if
requisite; above the rim of the mortar and between the pillars are six openings, twenty-four by ten inches,
which are covered by screens having 120 perforations to the square inch, through which the crushed
quartz and water must pass; above the screens boilerplate is screwed to the pillars so as to enclose the
battery; the weight of the twelve stampers is three ton or five hundred weight each; when at the maximum
speed each stamper makes sixty descents per minute, the battery striking 43,200 blows per hour; two and
a quarter tons weight of iron are at all times suspended upon the cams, nine being up and three down;
three tons rise and fall per second, 180 tons per minute, or 1080 tons per hour; it takes all this mighty
hammering to reduce twenty tons of quarts in twenty-four hours.
Having described the stamping operations, we will now endeavour to convey some idea of the manner
in which the gold is separated from the quartose sand. A frill or apron of sheet iron, twenty-two inches
broad, surrounds the battery, fitting under the drip flange; the frill is covered with blankets, over which the
sand passes into a trough. These blankets are removed and rinsed in tubs of clear water every four
hours. A large percentage of the precious metal is thus caught without further process, but it is
sometimes found necessary to effect a complete separation from the sand by means of an amalgamation
with mercury. From the trough the sand passes over a ripple board, four feet broad, with nine transverse
gutters half an inch deep, and three inches wide, four of which are filled with quicksilver. The sand passes
from the ripple board in two equal streams into the two tub amalgamators, where they again come into
contact with mercury, which an agitator, making fifty-eight revolutions a minute, keeps in constant motion.
Here a large proportion of the gold that escaped the blanket and the ripple board is secured; overflowing
from these amalgamators, the stand still leaving some gold, is carried through a spout to the Chilian basin,
five feet three inches in diameter; the bottom, made of cast iron, is six inches thick, and the aides are
formed of boiler plate iron. In this basin revolves two massive cast iron rollers, four feet six inches in
diameter, and eight inches broad, weighing together five tons, and working on oscillating axles fitted to a
vertical crown wheel shaft, which again is driven by a pinion on the main driving shaft. Three rollers
travel round the basin thirteen times in each minute; they answer two purposes-the one, that of grinding the
quartzose sand still finer; the other that of amalgamating by compression; and so for they have proved
themselves to be the best amalgamators yet invented, although they undoubtedly are the cause of the loss
of a large quantity of quicksilver. From the Chilian rollers, the sand, now supposed to have left all its
gold behind, passes by a trough into a large amalgamating tub, in which the agitators revolve with
less rapidity; from this tub the water and tailings flow into the creek. The whole of these works are driven by
a water-wheel, eighteen feet in diameter, estimated at eighteen-horse power, which is one-third more than
is requisite. The water is supplied by a race, four feet wide, two feet deep, and one mile in length, derived
from the Adelong Creek.
This machine has been in active operation since June last, has crushed 900 tons, which on the
average has yielded about five ounces per ton, and is owned by a limited liability company, consisting of
four shares; its value is about £1500, No breakage has occurred, and there is little wear, excepting of the
stampers and shoes, of which about two and a half tons have
been replaced. The cost of working, including repairs and loss of quicksilver, amounts to £50 per week; and
the income, on the average, not excluding stoppages, has been £150 per week; but as there are seven
other mills in operation, and five building, and as the supply of quartz does not keep pace with the means
of reducing it, it is anticipated that in future the profits derived from quartz crushing on the Adelong will not
be so great as they have been. The amalgam is retorted at these works in the manner already described.
A few hundred yards down the stream we arrive at the Union, water-power, driving one battery, and
crushing from three to four tons in twenty-four hours. Two additional batteries are about to be added to this
machine. In the neighbourhood is the mill of Edwards and Shannon, nearly completed, intended to be
worked by a water-wheel. A few yards further stands the Victoria, eight horse-power steam, driving a
battery of eight stampers, and crushing from four to five tons daily. On the hill to the right, in Williamstown,
is the Perseverance, eight horse-power steam, crushing its own quartz, and below the falls on the point a
new watermill is in the course of erection. About a mile lower still, under Gibraltar reef, you reach the
last mill on the stream. This machine is capable of crushing from three to four tons per day, and trusts
to the reef above for its supply of quartz. Water, power, sufficient to drive two additional mills, could be
obtained from the falls, and as the stream is permanent it is probable that, when the price of crushing
comes to be reduced by competition, and the scarcity of quartz, that those machines, driven by water-
power, will prove to be the most profitable investment.
The scarcity of useful timber, and the enormous expenses attending the carriage of heavy machinery
to this out-of-the-way place, has enhanced the cost of the erection of the mills on the Adelong. I am
informed that the gross outlay has been nearer £20,000 than the sum I formerly stated.