The First Burra Smelter

One month after work began at the Burra Burra Mine in September 1845 the directors of the South Australian Mining Association (SAMA) had decided to erect their own smelter on the mine site. In October 1845, they engaged Georg Ludwig Dreyer and his son, immigrants from the Harz Mountains in Hanover, to take charge of smelting operations similar to those used in their homeland under the supervision of Dr Ferdinand von Sommer. They would build a blast furnace fuelled by charcoal that could be produced from the colony’s forests rather than use imported coal. This furnace was to be erected between flanking brick piers against a wall within the Burra Mine store yard.

With construction underway early in January 1846 Henry Ayers, the Secretary of SAMA advertised for 25,000 bushels (over 600 tonnes) of charcoal and contracted with John Bagg a brick maker working at the mine for the supply of ‘100,000 good well burned bricks.’ These bricks were supplied by G.H. Ramsay & Co. of Newcastle on Tyne.

In March of the same year, the smelting house measuring 105 feet by 35 feet was under construction and very large bellows to supply the blast of air into the furnace were being built by James Marshall, an organ builder, in Adelaide. Unfortunately because of a shortage of bricks it was not until October 1847 that these preparations were completed and the first smelting could be attempted. This first trial resulted in about 4cwt (200kg.) of smelted copper matte. A witness reported that the copper ore was first roasted by heaping it on burning logs of wood and then it was added to the furnace with charcoal and a little limestone (calcium carbonate) as a flux and in three hours the copper was run off into moulds, the slag being less dense having been easily separated. One more process would be needed to refine the metal. It was clear at this stage that the process with two horses driving a whim, seriously distressing them, could not provide the necessary blast of air.

A second blast furnace was built by Dreyer with a similar result being described as follows:

The First Smelting Works by Frank Treloar

Some months before the visit of the Directors, arrangements were entered into with a Mr. Dreyer, who claimed to have had experience in smelting in Germany, to go to Burra, erect a small furnace there and carry out trial runs to prove if smelting could be carried out in Burra on more extensive lines. The structure was well advanced when Mr. Burr took office, On its completion it was a small furnace which held the charge and a large pair of bellows supplied the blast and driven off by a whim worked by either bullocks or horses and when working smoothly and satisfactorily it was supposed to put through eight hundred weight of copper a day.

The mechanism of the whym, or gin, generally used to haul ore out of the mine

The Furnace Trials - A Costly Failure

When Mr. Dreyer declared it ready for a start plenty of hands were standing nearby either ready to help or out of curiosity. Horses were used on the whim and after a run of 22 hours; about four cwt. of rough copper was produced. It was then found necessary to withdraw the charge and repair the bellows and fixings, which had suffered, badly by the trial. Several days later repairs being effected, another start was made with much the same results except that the horses were very distressed. More time passed in repairs and still another trial was made but the effort to keep up a constant blast was absolute cruelty to the horses besides shaking the bellows to pieces. This ended any further attempts at smelting under those conditions and just what the experiment cost would be hard to say, but from first to last could be classed a costly failure.

Treloar’s account comes from the records of the Burra Burra Mine that he rescued from the abandoned mine offices in 1929.

Dreyer suggested that a steam-driven blower be substituted for the horse-driven bellows. That would have necessitated the importing of a steam engine from England, something the directors of the company would be faced with, though for a different purpose, in the future.

Apparently the Burra Directors were unimpressed. On the 13th of Oct. 1847 they discontinued the smelting and dismissed all workers on the grounds that the operation was too expensive.

In Feb 1850, the smelting works had been converted to another use.

‘A yard is now walled around for the carpenters and the old smelting house into a workshop for their use. On the opposite side is the store.’

Why Dreyer’s Smelting Experiment Failed

Georg Dreyer had 22 years experience smelting the ores from the Harz Mountains in Hanover. These ores were sulphide ores unlike the hydrated carbonate ores of the Burra Burra Mine. Passing a blast of hot air through sulphide ores produced its own heat which sustained the smelting process. When heating Burra’s carbonate ores, rather than producing heat, they absorbed heat which cooled the mixture and slowed the reducing reaction. This is why Dreyer had to redesign his original blast furnace and force more air through the charge in a second experimental blast furnace. Unfortunately he was not able to force enough air through the charge and very nearly killed the poor horses driving the whim in the process.

With the advantage of hindsight, Dreyer’s blast furnace was ahead of its time, because it used exactly the technology now used in modern blast furnaces in steel production. Frank Treloar was merely reflecting the view of Henry Ayers, as he used SAMA’s Mine records as his source of information. Furthermore, the use of limestone as a flux, which is also common with modern smelters, would have meant that Burra’s carbonate ores that were won from dolomite, calcium magnesium carbonate, base rock had a ready supply of flux close by. The limestone would need to be first calcined converting it to lime (calcium oxide)