Chambers's Edinburgh Journal, No. 458, page 39 by Various Authors
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of copper. We don't care much about it; we seldom have it; but it is sold at the ticketings regularly. For want of a better name, we term it slag; but it is not slag, properly so called, which you see all around you. A better denomination is that employed in designating it in the Journal--namely, rubbish.'[5]
'You make no kind of distinction in the ore-yard,' we continued. 'Is that unnecessary?'
'Well, practically it is. As these heaps lie, you can perceive that a vertical slice from top to bottom will give us a tolerably even admixture of the different ores. This is always desirable to a certain extent, since the ores being of different constitution, the one materially assists in the reduction of the other. Thus an ore containing a large proportion of fluor-spar may with great advantage be employed to flux another containing felspar or quartz, which substances are almost infusible alone. Indeed, the judicious admixture of ores constitutes the most important vocation of the smelter; and it is to this that the copper-houses of Swansea are indebted for one of their advantages over the proprietors of mines, who, possessing only one kind of ore--rich, probably, but intractable--can never bring it into the state of a metal with any satisfactory profit.'
'What is the value of these ores?'
'That varies much. This gray sulphuret contains about 70 per cent. of copper, and is worth L.35 per ton. This yellow sulphuret, from being mixed with a large quantity of iron and silicious earth, contains only about 12 or 14 per cent. Some malachites contain so much as 50 per cent., and others less pure, 30 to 40 per cent. of copper. But the greater mass of the ores we melt have a far less produce than this. That Cornish ore you see there, for example, contains only 4-1/2 per cent. of metal. The average produce, however, of all the British and foreign ores smelted at Swansea may be given at about 12 per cent. Previous to the great increase of foreign importation, it was much lower.' < previous next >