(The Welshman. Dec 5, 1862)

Hitherto the extraction from its ores has been chiefly effected at Swansea by the use of large quantities of coal, but lately great improvements have been made in the treatment of sulphuret ores by what is called the “web process,” or cementation (requiring very little coal, and can, therefore, be used at the mines), which is now advancing very much, and promises to be a most important and economical mode of getting out the copper. It has been used in Spain, Germany, and Italy to a considerable extent, but the improvements in the process which have been lately made in England are very important, and will, when carried out at the different mines at home and abroad, where large quantities of sulphuret of copper ores can be obtained, although of a low percentage, be most important, and may hace a considerable effect on the copper trade.

In the province of Huelva, in Spain, there are several mines where immense masses of sulphuretted copper ores are found ; these ores contain 48 to 50 per cent. sulphur, and 3 to 6 per cent. copper, wet assay. Those mines which are near enough to the sea, like the St. Domingo and Tharsis, have shipped these ores to England, where they have first been sold to the sulphuric acid makers for the sulphur they contain, & after the acid makers have burn out the sulphur, & converted it into sulphuric acid, they return the burnt ore to the merchant, who then sells it to the copper smelter. But there are many other mines in Spain which are too far from the sea, and at these mines the copper is extracted from the ores by this cementation process. Amongst them may be named the Rio Tinto Mines (about 20 miles from Seville), the property of the Spanish Government ; the ores there are from 3 to 6 per cent., wet assay. The plan there pursued is, that the ore is raised from the mine at a cost of 3s to 4s per ton, and then it is delivered to contractors, who engage to work it, and for every ton of copper they receive £40, whereby a large profit is realised by the mine.

The process consists in first calcining the ores in large heaps on the ground, to burn off the sulphur, and which has the effect of converting the insoluble sulphuret into soluble sulphate of copper. The burnt ore is then put into large tanks with water, which dissolves out the sulphate ; this solution is then run into other tanks, in which pigs of iron are placed, and the copper is precipitated on the iron, from which it is afterwards stripped off, and then by once smelting a marketable copper is obtained. This process answers well, and by the Spanish Government’s annual reports it will be seen that they realise a large profit from the mines by its working. But a considerable quantity of copper is left behind in the ore, and, therefore, many persons have been trying experiments to improve on the process, and very many patents have been taken out in England for the purpose. Mr Bethell has been engaged on extensive experiments for some time, which have been so successful that he has erected large works in Cheshire for extracting copper from these Spanish ores after the sulphur in them has been burnt out by the sulphuric acid makers, and it is stated that by his process, as now improved, he can at a moderate cost extract all the copper to within ¼ per cent. wet assay.