The one piece of 'slag' recovered turned out to be vitrified ore mineral. There were no tuyeres and once again it is suggested that the air was supplied through blow pipes. Thus the evidence suggests that the earliest smelters followed on from the crucible melting of native copper. The ores would have been crushed and only the very richest fragments selected and placed in the crucible buried under charcoal in a hearth otherwise indistinguishable from a domestic hearth. The relatively high temperatures and reducing conditions necessary would have been achieved by the use of charcoal as.
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During a process lasting only a very few hours, some of the copper mineral would have been reduced to metal, some would have formed a slaggy vitrified material typically containing the oxides of copper and of iron, and much of the rest would just have calcined, such that the debris would be almost indistinguishable in the archaeological record except through careful excavation. The evidence for this proposed crucible process is necessarily ephemeral, or based on negative evidence ; the lack of tuyeres is taken as evidence for blow pipes on many sites, for example, but does seem to form a coherent picture across the Mediterranean, southern Europe and the Middle East.
There is one apparent exception, Timna, in southern Israel, where it is claimed there is evidence of smelting from the Neolithic, producing quantities of slag from furnaces with air supplied from bellows through tuyeres. These are the sites of F 2, which produced slags and tuyere fragments, and F 39 which also produced quantities of slag and the remains of a furnace The problem is not so much the nature of the material but with the very early dates ascribed to the two sites.
The excavation of F 2 was supervised by the author of this review, and was a typical desert site with a very truncated stratigraphy. The site lies in the general vicinity of much Late Bronze Age smelting activity and slag scatters are fairly common over the whole area. Most of the finds came from the surface or just a very few cm beneath, and included a range of material from palaeolithic flints to modern cartridge cases. The bulk of the material comprised slag, tuyere fragments, coarse pot sherds, flint tools and spills and prills of copper metal. In addition there was a small copper needle made of non-local copper with a composition typical of that used by the Chalcolithic Ghassulian culture.
In the centre of the areas excavated was the only feature to survive fig. The surrounding layer beneath the surface was heavily stained with charcoal and contained much broken slag as well as the prills of copper. It is important to keep in mind.
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This was almost certainly a melting hearth, where the prills of copper, extracted from the broken up slags, were melted and refined. It is very likely that the surficial slags and tuyere fragments also belong to this operation, the slags having been broken up to recover more copper prills and the tuyere to channel the air. Very recently a TL determination on a piece of the slag has confirmed the Late Bronze Age dating for the smelting debris The site of F 39B is a small stone built enclosure on a hill top, containing the remains of a small furnace, slag and flint tools were found in the vicinity The sample was of charcoal taken from the furnace wall itself and submitted by Barbetti and Rothenberg.
The sample apparently came from a small hollow near to a house in another enclosure, F 39 A, which lies over m from F 39B. Thus in no way does the new radiocarbon determination date the furnace. A more plausible explanation is that the enclosures are Chalcolithic, and may have been associated with metallurgy at that time, but the furnace and slag remains are of a much later period.
Thus with both of these sites there are serious problems with the stratigraphical relationships between the dated material and the putative early metallurgy. As the latter included quantities of true smelting slag, furnaces and tuyeres, all products of quite advanced smelting processes not encountered anywhere else for another two millennia, it would seem best to set aside these sites as representing the inception of extractive metallurgy. This controversy is unfortunate, and as a result the real evidence of early smelting from Timna, of the Early Bronze Age, see below, has been largely overshadowed.
Evidence for the new process has been found at a growing number of excavated sites, confirming the dates previously suggested by the rise in iron content of the copper. The ore was now smelted in small furnaces, the first pyro- technical structures specifically built for metallurgy. They were designed and sited to take full advantage of prevailing local winds, bellows were apparently still not used, at least in the smelting furnaces.
Although the principles of the furnaces. Note the furnaces were very carefully sited just below the top of the slope, and successive rebuilds occupied the same position. Photo, by courtesy of A. The evidence from selected sites around the eastern Mediterranean and Middle East are summarised below. The most comprehensively investigated sites are in the Wadi Feinan on the east side of the Wadi Arabah, in southern Jordan As described above, during the preceding Chalcoli- thic period copper oxide and hydroxy ores coming from sandstone had predominated in a crucible process, but now a different ore was exploited, chrysocolla, copper silicate, coming from dolomite limestone shales.
The problem with these ores was that it was impossible to manually separate the silica which was bound to the copper at molecular level. However the ores did have a particular advantage, especially to those developing a slag technology, in that the waste material associated with the copper minerals was rich in manganese oxides, which form a liquid slag of manganese silicates much more easily than with the more prevalent iron minerals.
The slags form under much less rigorous reducing conditions and are much less viscous than the corresponding iron slags. The typical smelter is now located by scatters of manganese-rich slags on hill tops. In and under these scatters are the remains of the small furnaces built into the steep slopes of hills just beneath the very summit and clearly very carefully set into the prevailing winds. The furnaces are set in lines following the contours very precisely to within a few cm fig.
The furnaces seem to be of two types, some were made of stone slates, loosely stacked to form a small shaft through which the wind could easily penetrate, now represented by scatters of slate fragments fused by slag fig. Others, mainly found on hills that lacked the necessary slates were of clay, frequently relined and reused, built into the hillsides.
Their fronts, facing into the wind, are now missing and were apparently open.
However, scattered all around are small fingers of burnt clay, often partially vitrified and with runnels of slag which showed that the fingers had been upright while the smelt was in progress. This suggests that the fingers in some way contained the furnace charge at the front of the furnace. Hauptmann believes they were actually set inside the front furnace wall, to strengthen it and indeed a very few have been found set in clay, but the vast majority seem to have been free standing, as if to create some form of grill. These wind powered furnaces must have generated only moderately reducing conditions as evidenced by the slags which are from a much.
Ras en Naqab, Feinan. For some time Feinan was the only known example of these primitive wind-blown furnaces, apart from very similar finds at Timna on a hilltop, designated site There some of the clay fingers were found actually fused to crucible fragments, suggesting a possible transition from the earlier crucible smelting process.
Egyptian influence in Sinai and at Timna must always have been strong, and now there is evidence of wind-blown furnaces from between the Eastern Desert and the Gulf of Suez in the Wadis Um Balad and Dara fig. The ore was a low grade mixture of copper oxides, malachite and chrysocolla contained in a vein material of silica and calcite. The furnaces were carefully positioned just below the crest of steep ridges and faced into the prevailing winds.
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The backs and sides of the furnaces were preserved and were of stone. As at Feinan the front is always missing and seems to have been separate from the rest of the furnace, but here there is no surviving indication of what might have constituted the front.
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Something would have been necessary if only to hold the furnace charge in place. The excavators suggested that iron oxides may have been deliberately added as a slag former, certainly the slags are iron-rich, containing iron spinels and pyroxenes, with the minerals magnetite and fayalite together with iron and calcium silicates. In order to release the copper the slags were taken down into workshops in the valley and finely crushed, and the prills melted in nearby small furnaces. These were probably supplied with air from blowpipes. No tuyeres or blow pipe tips were found, but the melting furnaces were surrounded by stone benches on which the excavators believed the blowers sat.
The ores were polymetallic, copper and lead, themselves rich in other metals such as arsenic, antimony, nickel and silver which were carried through the smelting process and into the metal.
Copper sulphide ores were also present which the excavators believe were also being smelted at this early date, suggesting that a preliminary roasting of the ore may have been carried out to reduce the sulphur content. The diversity of ores is reflected in the slags, including copper slag containing magnetite and fayalite with droplets of copper-iron sulphide, a glassy slag with droplets of argentiferous lead, and a third rich in droplets of nickel-arsenide, that is a speiss.
The slags were concentrated in and around buildings described as workshops, together with ore fragments, stone grinding tools and crucible fragments, but apart from some burnt hollows there was no indication of furnaces, and once again tuyeres were not found, suggesting the pyrotechnical operations may have been fed with air through blow pipes. A number of sites of copper smelting have recently been investigated dating from the Early Bronze Age. The site of Sideri on Kythnos has produced scatters of ore, slag and furnace fragments. The ore was mainly malachite and azurite.
The clay furnace fragments, typically about 4 cm thick could be reconstructed into a cylindrical furnace approximately 50 to 55 cm in diameter. The furnace fragments contained numerous holes about 2. Recent discoveries have also been made on Crete of small wind-blown furnaces at Chrysokamino in the north east of the island.
The smelting site was evidenced by scatters of crushed slag and furnace fragments, some slagged, situated about m from the contemporary settlement. The furnaces were carefully sited in a small gap between two peaks near to the sea to take advantage of the wind. The fragments of furnace walls indicated a free-standing cylindrical furnace and were of clay perforated with many holes to allow the wind to penetrate. The site is far away from known ore sources and it is. Granodiorite bedrock. Rear wall of furnace. Layer of silt. Straw -tempered silt lining. Vitrified lining in situ. Residues of lining.
Plan only a. The slags were finely crushed to recover the prills of copper but the absence of crucibles or moulds suggests that the metal was fabricated elsewhere. The development of metallurgy from the Neolithic through to the Bronze Age in the eastern Mediterranean and Middle East was largely based on developments in pyrotechnology that fundamentally changed man's relationship with fire. After a million years or so of uncontrolled bonfires, man, by the successive use of specially prepared fuels, structures for containing the fire and control of the air supply was able to vastly extend the range of temperature and reducing.
Real pyrotechnology had arrived. It has often been suggested that developments in ceramic technology, particularly in the kilns believed to be necessary for the firing of painted pottery, led to the discovery of metal smelting. However the conditions necessary to smelt copper are very different and the earliest surviving furnaces are very different in shape and size from any pottery kiln.
The processes of extending and controlling fire proceeded in stages over several millennia in parallel with developments in producing lime plaster and pottery, both of which also required controlled conditions, but at significantly lower temperatures than for metals.