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 The following article ‘Choice of Gold Mining Machinery’ was written by Donald Clarke and appeared in The Australian Mining Standard, 25th February 1904:
“The following furnishes approximate prices for the cost of a mill for any out-of-the-way mine on the lines previously suggested:
20 N.H.P. Cornish flue boiler for 100lb. working pressure............L200
30N.H.P. Cornish flue boiler for 100lb. working pressure............. 275
20N.H.P. Horizontal slide valve engine, with governor...............275
Compound engine, with governor, complete...........................350
10-head iron framed battery, 1100lb Stamps
5-head belt driven from underneath counter
shaft, with cross-keyed tappets, etc.,
complete..............................................................600
Copper plate tables, with 20 feet copper for each 5-head........... 40
30-inch Berdan pan and framing complete............................... 20
Concentrating table, complete............................................125
Grinding pan, 4 feet 6 inches diameter.................................. 50
The cost of a suitable stonebreaker would amount to from L50 to L70.
An Automatic ore feeder could be made for L10 complete.
In addition to this shafting, belting, and pulleys would absorb L120. The cost of carriage, shed, and foundations, and erection would cost as much as half as the plant. Roughly speaking, a 10-head battery, with appliances indicated, would cost from L1000 to L1500.
Ordinary battery practice does not need much discussion. The work for the most part simple and mechanical. In Victoria, especially at Bendigo, crushing is cheaply done, but costs would be a good deal less than they are if stonebreakers, feeders and more modern types of batteries were erected. For small mills it is of no use procuring extra machinery where the same number of men are employed with or without it, unless the extra machinery means a reasonable reduction of costs per ton.
No 10-head or larger battery, crushing regularly, should be without a stonebreaker, grizzly and automatic feeders. The stamps, as before indicated, should be not less than 1000lb. in weight. Whether inside amalgamation by means of copper plates is practised in the box or not is largely a matter of taste. In general it is advisable to feed mercury into the box except with heavily mineralised ores. The amount fed in should be 2 and a half times the weight of gold liberated. That is, if stone is crushing 2oz. per ton, and a ton is crushed in a 5-head battery in an hour, then 2 x 2 and a half, or 5oz., of mercury should be fed in per hour. If the stone runs one ounce per ton, then 5oz. mercury in two hours will suffice. An even, regular feed along the length of the box should be supplied. The state of the outside plate will generally indicate the proper amount to feed in; if the plate is sloppy, to much is passing into the box; if dry too little. Very little care is usually exercised in packing a box; in many cases the rubbish from the last clean up is shavelled back again, making the box foul from the start. Clean, angular pieces should be wedged between the dies, leaving room for any gold or amalgam to lodge. Amalgam will always get into every crevice in a rich crushing, and the provisions made by some makers in having liners with ripples cast in them appears to be good, although I never had any experience with them. From 3 to 5 gallons of water per stamper per minute are used in ordinary practice; in this matter it is better to use about two-thirds of the total amount by supplying each stamp evenly and to supply the remainder or one-third after the sand has left the first copper plate. The pulp will not be thinned too much in the box; most of the amalgam passing through the screens will be caught on the top plate, the overflow from the box serving to carry it this far in a series of pulsations. The water to prevent the lodgement of sand on the remaing plates can be evenly supplied across the table. If plates are properly laid, well amalgamated, and tended to, wells are unnecessary.
All that need be said about concentration of gold ore is that concentrators which are well adapted for saving minerals of high specific gravity will not do corresponding work on gold ores..........”
It is clear why very few small mines had their own battery due to the expenses involved in doing so. The costs being prohibitive to a single operator or small partnership of working miners batteries were the province of mines that could attract capital, generally from local shareholders, or large No-Liability companies set up to work the more profitable mines. Some areas had independent batteries, particularly the early years at Yalwal, who would crush anyone’s ore for a fee or a percentage of yield. Often the the smaller mines bagged up their ore and sent it to a smelting works for treatment, either Clyde, in Sydney, or later to the Dapto Smelting Works. The drawback to this of course was that the lesser grades were not worth sending and were left at grass.
The supply of water to the battery was also an ongoing problem with many mines having to suspend work for months on end during periods of drought. With a 5-head battery requiring an average of 20 gallons of water per minute, this meant that it using 9600 gallons (over 36000 litres) per eight hour shift !
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