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ORE PROCESSING IN THE LATE 19th CENTURY
The diagram below is a summary of the process used at Alderley Edge. Click on the boxes to get a fuller description of each step. This process was quite economical as it used acid and did not require much fuel. Most copper mines had to process their ore in three stages: roasting, smelting and refining, but at Alderley Edge, the nature of the ore meant that only one chemical process and smelting were required. You can also read about how to carry out the process at home.
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Extraction
Ore is removed from the mine by tramway from West Mine or the Hough Level. The trucks were pulled up into the treatment plant using a steam engine and winch.
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Crushing the ore
The ore was crushed to less than 1/2 inch size through Cornish rolls. These consist of two rollers, rather like a mangle on its side. The rolls are set 1/2 inch apart so that all rock must be that size or smaller after crushing.
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Loading the vats
Ore was taken by truck and tipped into one of 16 empty wooden or slate vats. The vats were prepare d with a layer of brushwood at the bottom so that acid poured in would drain through the sand and could be removed from the bottom.
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Leaching
The ore was washed with acid and water which leached out the copper solution. The leaching involved recirculating acid through the tanks and then washing the sand with clean water. All the washings were saved and reused. This part of the process is described in more detail on another page.
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Transfer
Copper solution from the leaching vats was transferred to another vat. The solution was pumped away into another set of wooden vats.
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Scrap iron
Scrap iron is put into the vat which precipitates copper through ion exchange. Ion exchange means that copper bound into the acid is released and becomes copper metal while the iron metal becomes iron salts, iron chloride if hydrochloric acid is used. The process takes place spontaneously.
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Drying
Periodically, the copper was removed and dried. The residue was washed first to try to get rid of as much iron as possible. We do not know where the iron-rich residue went but it was probably tipped into the stream running down Pickhill Lane.
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Smelting
The dried copper (about 60-70% pure) was sent away for smelting and purifying. Most of the copper went to St Helens although there was also a smelter at Warrington.
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