De Re Metallica · Georg Agricola
Our best evidence of ancient lead-silver metallurgy is the result of the studies at Mt. Laurion by Edouard Ardaillon (Mines du Laurion dans l'Antiquite, Paris, 1897). Here the very extensive old workings and the slag heaps testify to the greatest activity. The re-opening of the mines in recent years by a French Company has well demonstrated their technical character, and the frequent mention in Greek History easily determines their date. These deposits of argentiferous galena were extensively worked before 500 B.C. and while the evidence of concentration methods is ample, there is but little remaining of the ancient smelters. Enough, however, remains to demonstrate that the galena was smelted in small furnaces at low heat, with forced draught, and that it was subsequently cupelled. In order to reduce the sulphides the ancient smelters apparently depended upon partial roasting in the furnace at a preliminary period in reduction, or else upon the ferruginous character of the ore, or upon both. See notes p. 27 and p. 265. Theognis (6th century B.C.) and Hippocrates (5th century B.C.) are frequently referred to as mentioning the refining of gold with lead; an inspection of the passages fails to corroborate the importance which has been laid upon them. Among literary evidences upon lead metallurgy of later date, Theophrastus (300 B.C.) describes the making of white-lead with lead plates and vinegar. Diodorus Siculus (1st century B.C.), in his well-known quotation from Agatharchides (2nd century B.C.) with regard to gold mining and treatment in Egypt, describes the refining of gold with lead. (See note 8, p. 279.) Strabo (63 B.C.-24 A.D.) says (III, 2, 8): "The furnaces for silver are constructed lofty in order that the vapour, which is dense and pestilent, may be raised and carried off." And again (III, 2, 10), in quoting from Polybius (204-125 B.C.): "Polybius, speaking of the silver mines of New Carthage, tells us that they are extremely large, distant from the city about 20 stadia, and occupy a circuit of 400 stadia; that there are 40,000 men regularly engaged in them, and that they yield daily to the Roman people (a revenue of) 25,000 drachmae. The rest of the process I pass over, as it is too long; but as for the silver ore collected, he tells us that it is broken up and sifted through sieves over water; that what remains is to be again broken, and the water having been strained off it is to be sifted and broken a third time. The dregs which remain after the fifth time are to be melted, and the lead being poured off, the silver is obtained pure. These silver mines still exist; however, they are no longer the property of the State, neither these nor those elsewhere, but are possessed by private individuals. The gold mines, on the contrary, nearly all belong to the State. Both at Castlon and other places there are singular lead mines worked. They contain a small proportion of silver, but not sufficient to pay for the expense of refining" (Hamilton's Trans.). Dioscorides (1st century A.D.), among his medicines, describes several varieties of litharge, their origin, and the manner of making white-lead (see on pp. 465, 440), but he gives no very tangible information on lead smelting. Pliny, at the same period in speaking of silver, (XXXIII, 31), says: "After this we speak of silver, the next folly. Silver is only found in shafts, there being no indications like shining particles as in the case of gold. This earth is sometimes red, sometimes of an ashy colour. It is impossible to melt it except with lead ore (vena plumbi), called galena, which is generally found next to silver veins. And this the same agency of fire separates part into lead, which floats on the silver like oil on water." (We have transferred lead and silver in this last sentence, otherwise it means nothing.) Also (XXXIV, 47) he says: "There are two different sources of lead, it being smelted from its own ore, whence it comes without the admixture of any other substance, or else from an ore which contains it in common with silver. The metal, which flows liquid at the first melting in the furnace, is called stannum that at the second melting is silver; that which remains in the furnace is galena, which is added to a third part of the ore. This being again melted, produces lead with a deduction of two-ninths." We have, despite some grammatical objections, rendered this passage quite differently from other translators, none of whom have apparently had any knowledge of metallurgy; and we will not, therefore, take the several pages of space necessary to refute their extraordinary and unnecessary hypotheses. From a metallurgical point of view, two facts must be kept in mind,--first, that galena in this instance was the same substance as molybdaena, and they were both either a variety of litharge or of lead carbonates; second, that the stannum of the Ancients was silver-lead alloy. Therefore, the metallurgy of this paragraph becomes a simple melting of an argentiferous lead ore, its subsequent cupellation, with a return of the litharge to the furnace. Pliny goes into considerable detail as to varieties of litharge, for further notes upon which see p. 466. The Romans were most active lead-silver miners, not only in Spain, but also in Britain. There are scores of lead pigs of the Roman era in various English museums, many marked "ex argent." Bruce (The Roman Wall, London, 1852, p. 432) describes some Roman lead furnaces in Cumberland where the draught was secured by driving a tapering tunnel into the hills. The Roman lead slag ran high in metal, and formed a basis for quite an industry in England in the early 18th century (Hunt, British Mining, London, 1887, p. 26, etc.). There is nothing in mediaeval literature which carries us further with lead metallurgy than the knowledge displayed by Pliny, until we arrive at Agricola's period. The history of cupellation is specially dealt with in note on p. 465.
Pliny (XXXIV, 33) appears somewhat confused as to the difference between the two species: "That which is called pompholyx and spodos is found in the copper-smelting furnaces, the difference between them being that pompholyx is separated by washing, while spodos is not washed. Some have called that which is white and very light pompholyx, and it is the soot of copper and cadmia; whereas spodos is darker and heavier. It is scraped from the walls of the furnace, and is mixed with particles of metal, and sometimes with charcoal." (XXXIV, 34.) "The Cyprian spodos is the best. It is formed by fusing cadmia with copper ore. This being the lightest part of the metal, it flies up in the fumes from the furnace, and adheres to the roof, being distinguished from the soot by its whiteness. That which is less white is immature from the furnace, and it is this which some call 'pompholyx.'" Agricola (De Natura Fossilium, p. 350) traverses much the same ground as the authors previously quoted, and especially recommends the pompholyx produced when making brass by melting alternate layers of copper and calamine (cadmia fossilis).
HISTORICAL NOTE ON GOLD.--There is ample evidence of gold being used for ornamental purposes prior to any human record. The occurrence of large quantities of gold in native form, and the possibility of working it cold, did not necessitate any particular metallurgical ingenuity. The earliest indications of metallurgical work are, of course, among the Egyptians, the method of washing being figured as early as the monuments of the IV Dynasty (prior to 3800 B.C.). There are in the British Museum two stelae of the XII Dynasty (2400 B.C.) (144 Bay 1 and 145 Bay 6) relating to officers who had to do with gold mining in Nubia, and upon one there are references to working what appears to be ore. If this be true, it is the earliest reference to this subject. The Papyrus map (1500 B.C.) of a gold mine, in the Turin Museum (see note 16, p. 129), probably refers to a quartz mine. Of literary evidences there is frequent mention of refining gold and passing it through the fire in the Books of Moses, arts no doubt learned from the Egyptians. As to working gold, ore as distinguished from alluvial, we have nothing very tangible, unless it be the stelae above, until the description of Egyptian gold mining by Agatharchides (see note 8, p. 279). This geographer, of about the 2nd century B.C., describes very clearly indeed the mining, crushing, and concentration of ore and the refining of the concentrates in crucibles with lead, salt, and barley bran. We may mention in passing that Theognis (6th Century B.C.) is often quoted as mentioning the refining of gold with lead, but we do not believe that the passage in question (1101): "But having been put to the test and being rubbed beside (or against) lead as being refined gold, you will be fair," etc.; or much the same statement again (418) will stand much metallurgical interpretation. In any event, the myriads of metaphorical references to fining and purity of gold in the earliest shreds of literature do not carry us much further than do those of Shakespeare or Milton. Vitruvius and Pliny mention the recovery or refining of gold with mercury (see note 12, p. 297 on Amalgamation); and it appears to us that gold was parted from silver by cementation with salt prior to the Christian era. We first find mention of parting with sulphur in the 12th century, with nitric acid prior to the 14th century, by antimony sulphide prior to the 15th century, and by cementation with nitre by Agricola. (See historical note on parting gold and silver, p. 458.) The first mention of parting gold from copper occurs in the early 16th century (see note 24, p. 462). The first comprehensive description of gold metallurgy in all its branches is in De Re Metallica.
By way of literary evidences, the following lines from Homer (Iliad, XVIII.) have interest as being the first preserved description in any language of a metallurgical work. Hephaestus was much interrupted by Thetis, who came to secure a shield for Achilles, and whose general conversation we therefore largely omit. We adopt Pope's translation:--
There the lame architect the goddess found Obscure in smoke, his forges flaming round, While bathed in sweat from fire to fire he flew; And puffing loud the roaring bellows blew. * * * In moulds prepared, the glowing ore (metal?) he pours. * * * "Vouchsafe, oh Thetis! at our board to share The genial rites and hospitable fare; While I the labours of the forge forego, And bid the roaring bellows cease to blow." Then from his anvil the lame artist rose; Wide with distorted legs oblique he goes, And stills the bellows, and (in order laid) Locks in their chests his instruments of trade; Then with a sponge, the sooty workman dress'd His brawny arms embrown'd and hairy breast. * * * Thus having said, the father of the fires To the black labours of his forge retires. Soon as he bade them blow the bellows turn'd Their iron mouths; and where the furnace burn'd Resounding breathed: at once the blast expires, And twenty forges catch at once the fires; Just as the God directs, now loud, now low, They raise a tempest, or they gently blow; In hissing flames huge silver bars are roll'd, And stubborn brass (copper?) and tin, and solid gold; Before, deep fixed, the eternal anvils stand. The ponderous hammer loads his better hand; His left with tongs turns the vex'd metal round. And thick, strong strokes, the doubling vaults rebound Then first he formed the immense and solid shield;
Even if we place the siege of Troy at any of the various dates from 1350 to 1100 B.C., it does not follow that the epic received its final form for many centuries later, probably 900-800 B.C.; and the experience of the race in metallurgy at a much later period than Troy may have been drawn upon to fill in details. It is possible to fill a volume with indirect allusion to metallurgical facts and to the origins of the art, from Greek mythology, from Greek poetry, from the works of the grammarians, and from the Bible. But they are of no more technical value than the metaphors from our own tongue. Greek literature in general is singularly lacking in metallurgical description of technical value, and it is not until Dioscorides (1st Century A.D.) that anything of much importance can be adduced. Aristotle, however, does make an interesting reference to what may be brass (see note on p. 410), and there can be no doubt that if we had the lost work of Aristotle's successor, Theophrastus (372-288 B.C.), on metals we should be in possession of the first adequate work on metallurgy. As it is, we find the green and blue copper minerals from Cyprus mentioned in his "Stones." And this is the first mention of any particular copper ore. He also mentions (XIX.) pyrites "which melt," but whether it was a copper variety cannot be determined. Theophrastus further describes the making of verdigris (see note 4, p. 440). From Dioscorides we get a good deal of light on copper treatment, but as his objective was to describe medicinal preparations, the information is very indirect. He states (V, 100) that "pyrites is a stone from which copper is made." He mentions chalcitis (copper sulphide, see note on, p. 573); while his misy, sory, melanteria, caeruleum, and chrysocolla were all oxidation copper or iron minerals. (See notes on p. 573.) In giving a method of securing pompholyx (zinc oxide), "the soot flies up when the copper refiners sprinkle powdered cadmia over the molten metal" (see note 26, p. 394); he indirectly gives us the first definite indication of making brass, and further gives some details as to the furnaces there employed, which embraced bellows and dust chambers. In describing the making of flowers of copper (see note 26, p. 538) he states that in refining copper, when the "molten metal flows through its tube into a receptacle, the workmen pour cold water on it, the copper spits and throws off the flowers." He gives the first description of vitriol (see note 11, p. 572), and describes the pieces as "shaped like dice which stick together in bunches like grapes." Altogether, from Dioscorides we learn for the first time of copper made from sulphide ores, and of the recovery of zinc oxides from furnace fumes; and he gives us the first certain description of making brass, and finally the first notice of blue vitriol.
The next author we have who gives any technical detail of copper work is Pliny (23-79 A.D.), and while his statements carry us a little further than Dioscorides, they are not as complete as the same number of words could have afforded had he ever had practical contact with the subject, and one is driven to the conclusion that he was not himself much of a metallurgist. Pliny indicates that copper ores were obtained from veins by underground mining. He gives the same minerals as Dioscorides, but is a good deal confused over chrysocolla and chalcitis. He gives no description of the shapes of furnaces, but frequently mentions the bellows, and speaks of the cadmia and pompholyx which adhered to the walls and arches of the furnaces. He has nothing to say as to whether fluxes are used or not. As to fuel, he says (XXXIII, 30) that "for smelting copper and iron pine wood is the best." The following (XXXIV, 20) is of the greatest interest on the subject:--"Cyprian copper is known as coronarium and regulare; both are ductile.... In other mines are made that known as regulare and caldarium. These differ, because the caldarium is only melted, and is brittle to the hammer; whereas the regulare is malleable or ductile. All Cyprian copper is this latter kind. But in other mines with care the difference can be eliminated from caldarium, the impurities being carefully purged away by smelting with fire, it is made into regulare. Among the remaining kinds of copper the best is that of Campania, which is most esteemed for vessels and utensils. This kind is made in several ways. At Capua it is melted with wood, not with charcoal, after which it is sprinkled with water and washed through an oak sieve. After it is melted a number of times Spanish plumbum argentum (probably pewter) is added to it in proportion of ten pounds of the lead to one hundred pounds of copper, and thereby it is made pliable and assumes that pleasing colour which in other kinds of copper is effected by oil and the sun. In many parts of the Italian provinces they make a similar kind of metal; but there they add eight pounds of lead, and it is re-melted over charcoal because of the scarcity of wood. Very different is the method carried on in Gaul, particularly where the ore is smelted between red hot stones, for this burns the metal and renders it black and brittle. Moreover, it is re-melted only a single time, whereas the oftener this operation is repeated the better the quality becomes. It is well to remark that all copper fuses best when the weather is intensely cold." The red hot stones in Gaul were probably as much figments of imagination as was the assumption of one commentator that they were a reverberatory furnace. Apart from the above, Pliny says nothing very direct on refining copper. It is obvious that more than one melting was practised, but that anything was known of the nature of oxidation by a blast and reduction by poling is uncertain. We produce the three following statements in connection with some bye-products used for medicinal purposes, which at least indicate operations subsequent to the original melting. As to whether they represent this species of refining or not, we leave it to the metallurgical profession (XXXIV, 24):--"The flowers of copper are used in medicine; they are made by fusing copper and moving it to another furnace, where the rapid blast separates it into a thousand particles, which are called flowers. These scales are also made when the copper cakes are cooled in water (XXXIV, 35). Smega is prepared in the copper works; when the metal is melted and thoroughly smelted charcoal is added to it and gradually kindled; after this, being blown upon by a powerful bellows, it spits out, as it were, copper chaff (XXXIV, 37). There is another product of these works easily distinguished from smega, which the Greeks call diphrygum. This substance has three different origins.... A third way of making it is from the residues which fall to the bottom in copper furnaces. The difference between the different substances (in the furnace) is that the copper itself flows into a receiver; the slag makes its escape from the furnace; the flowers float on the top (of the copper?), and the diphrygum remains behind. Some say that in the furnace there are certain masses of stone which, being smelted, become soldered together, and that the copper fuses around it, the mass not becoming liquid unless it is transferred to another furnace. It thus forms a sort of knot, as it were, in the metal."
Pliny is a good deal confused over the copper alloys, failing to recognise aurichalcum as the same product as that made by mixing cadmia and molten copper. Further, there is always the difficulty in translation arising from the fact that the Latin aes was indiscriminately copper, brass, and bronze. He does not, except in one instance (XXXIV., 2), directly describe the mixture of cadmia and copper. "Next to Livian (copper) this kind (corduban, from Spain) most readily absorbs cadmia, and becomes almost as excellent as aurichalcum for making sesterces." As to bronze, there is no very definite statement; but the argentatium given in the quotation above from XXXIV, 20, is stated in XXXIV, 48, to be a mixture of tin and lead. The Romans carried on most extensive copper mining in various parts of their empire; these activities extended from Egypt through Cyprus, Central Europe, the Spanish Peninsula, and Britain. The activity of such works is abundantly evidenced in the mines, but very little remains upon the surface to indicate the equipment; thus, while mining methods are clear enough, the metallurgy receives little help from these sources. At Rio Tinto there still remain enormous slag heaps from the Romans, and the Phoenician miners before them. Professor W. A. Carlyle informs us that the ore worked must have been almost exclusively sulphides, as only negligible quantities of carbonates exist in the deposits; they probably mixed basic and siliceous ores. There is some evidence of roasting, and the slags run from .2 to .6%. They must have run down mattes, but as to how they ultimately arrived at metallic copper there is no evidence to show.
The special processes for separating other metals from copper by liquation and matting, or of refining by poling, etc., are none of them clearly indicated in records or remains until we reach the 12th century. Here we find very adequate descriptions of copper smelting and refining by the Monk Theophilus (see Appendix B). We reproduce two paragraphs of interest from Hendrie's excellent translation (p. 305 and 313): "Copper is engendered in the earth. When a vein of which is found, it is acquired with the greatest labour by digging and breaking. It is a stone of a green colour and most hard, and naturally mixed with lead. This stone, dug up in abundance, is placed upon a pile and burned after the manner of chalk, nor does it change colour, but yet loses its hardness, so that it can be broken up. Then, being bruised small, it is placed in the furnace; coals and the bellows being applied, it is incessantly forged by day and night. This should be done carefully and with caution; that is, at first coals are placed in, then small pieces of stone are distributed over them, and again coals, and then stone anew, and it is thus arranged until it is sufficient for the size of the furnace. And when the stone has commenced to liquefy, the lead flows out through some small cavities, and the copper remains within. (313) Of the purification of copper. Take an iron dish of the size you wish, and line it inside and out with clay strongly beaten and mixed, and it is carefully dried. Then place it before a forge upon the coals, so that when the bellows act upon it the wind may issue partly within and partly above it, and not below it. And very small coals being placed round it, place copper in it equally, and add over it a heap of coals. When, by blowing a long time, this has become melted, uncover it and cast immediately fine ashes of coals over it, and stir it with a thin and dry piece of wood as if mixing it, and you will directly see the burnt lead adhere to these ashes like a glue. Which being cast out again superpose coals, and blowing for a long time, as at first, again uncover it, and then do as you did before. You do this until at length, by cooking it, you can withdraw the lead entirely. Then pour it over the mould which you have prepared for this, and you will thus prove if it be pure. Hold it with pincers, glowing as it is, before it has become cold, and strike it with a large hammer strongly over the anvil, and if it be broken or split you must liquefy it anew as before."
The next writer of importance was Biringuccio, who was contemporaneous with Agricola, but whose book precedes De Re Metallica by 15 years. That author (III, 2) is the first to describe particularly the furnace used in Saxony and the roasting prior to smelting, and the first to mention fluxes in detail. He, however, describes nothing of matte smelting; in copper refining he gives the whole process of poling, but omits the pole. It is not until we reach De Re Metallica that we find adequate descriptions of the copper minerals, roasting, matte smelting, liquation, and refining, with a wealth of detail which eliminates the necessity for a large amount of conjecture regarding technical methods of the time.
CHARGE. PRODUCTS.
{ Crude ore 5,400 lbs. } Primary matte (1) 600 lbs. { Lead slags 3 cartloads } 1st { Schist 1 cartload } Silver-copper alloy (A) 50 " { Flux 20 lbs. } { Concentrates from } Slags (B) { slags & accretions Small quantity }
{ Primary matte (1) 1,800 lbs. } Secondary matte (2) 1,800 lbs. { Hearth-lead & litharge 1,200 " } { Lead ore 300 " } Silver-copper-lead 2nd { Rich hard cakes (A{4}) 500 " } alloy (liquation { Liquated cakes 200 " } cakes) (A{2}) 1,200 " { Slags (B) } { Concentrates from } Slags (B{2}) { accretions }
{ Secondary matte (2) 1,800 lbs. } Tertiary matte (3) 1,300 lbs. { Hearth-lead & litharge 1,200 " } Silver-copper-lead { Lead ore 300 " } alloy (liquation 3rd { Rich hard cakes (A{4}) 500 " } cakes) (A{3}) 1,100 " { Slags (B{2}) } Slags (B{3}) { Concentrates from } { accretions }
{ Tertiary matte (3) 11 cartloads } Quaternary hard cakes { Poor hard cakes (A{5}) 3 " } matte (4) 2,000 lbs. 4th { Slags (B{3}) } Rich hard cakes of { Concentrates from } matte (A{4}) 1,500 " { accretions }
{ Roasted quartz } Poor hard cakes of 5th { Matte (4) (three } matte (A{5}) 1,500 lbs. { times roasted) 11 cartloads } Final cakes of matte (5)
6th Final matte three times roasted is smelted to blister copper.
The following would be a rough approximation of the value of the various products:--
(1.) Primary matte = 158 ounces troy per short ton. (2.) Secondary matte = 85 " " " (3.) Tertiary matte = 60 " " " (4.) Quaternary matte = Indeterminate. A. Copper-silver alloy = 388 ounces Troy per short ton. A{2} Copper-silver-lead alloy = 145 " " " A{3} " " " = 109 " " " A{4} Rich hard cakes = 97 " " " A{5} Poor hard cakes = Indeterminate. Final blister copper = 12 ozs. Troy per short ton.
HISTORICAL NOTE ON ZINC. The history of zinc metallurgy falls into two distinct lines--first, that of the metal, and second, that of zinc ore, for the latter was known and used to make brass by cementation with copper and to yield oxides by sublimation for medicinal purposes, nearly 2,000 years before the metal became generally known and used in Europe.
There is some reason to believe that metallic zinc was known to the Ancients, for bracelets made of it, found in the ruins of Cameros (prior to 500 B.C.), may have been of that age (Raoul Jagnaux, Traite de Chimie Generale, 1887, II, 385); and further, a passage in Strabo (63 B.C.-24 A.D.) is of much interest. He states: (XIII, 1, 56) "There is found at Andeira a stone which when burnt becomes iron. It is then put into a furnace, together with some kind of earth, when it distils a mock silver (pseudargyrum), or with the addition of copper it becomes the compound called orichalcum. There is found a mock silver near Tismolu also." (Hamilton's Trans., II, p. 381). About the Christian era the terms orichalcum or aurichalcum undoubtedly refer to brass, but whether these terms as used by earlier Greek writers do not refer to bronze only, is a matter of considerable doubt. Beyond these slight references we are without information until the 16th Century. If the metal was known to the Ancients it must have been locally, for by its greater adaptability to brass-making it would probably have supplanted the crude melting of copper with zinc minerals.
It appears that the metal may have been known in the Far East prior to such knowledge in Europe; metallic zinc was imported in considerable quantities from the East as early as the 16th and 17th centuries under such terms as tuteneque, tuttanego, calaem, and spiauter--the latter, of course, being the progenitor of our term spelter. The localities of Eastern production have never been adequately investigated. W. Hommel (Engineering and Mining Journal, June 15, 1912) gives a very satisfactory review of the Eastern literature upon the subject, and considers that the origin of manufacture was in India, although the most of the 16th and 17th Century product came from China. The earliest certain description seems to be some recipes for manufacture quoted by Praphulla Chandra Ray (A History of Hindu Chemistry, London, 1902, p. 39) dating from the 11th to the 14th Centuries. There does not appear to be any satisfactory description of the Chinese method until that of Sir George Staunton (Journal Asiatique Paris, 1835, p. 141.) We may add that spelter was produced in India by crude distillation of calamine in clay pots in the early part of the 19th Century (Brooke, Jour. Asiatic Soc. of Bengal, vol. XIX, 1850, p. 212), and the remains of such smelting in Rajputana are supposed to be very ancient.
The discovery of zinc in Europe seems to have been quite independent of the East, but precisely where and when is clouded with much uncertainty. The marchasita aurea of Albertus Magnus has been called upon to serve as metallic zinc, but such belief requires a hypothesis based upon a great deal of assumption. Further, the statement is frequently made that zinc is mentioned in Basil Valentine's Triumphant Chariot of Antimony (the only one of the works attributed to this author which may date prior to the 17th Century), but we have been unable to find any such reference. The first certain mention of metallic zinc is generally accredited to Paracelsus (1493-1541), who states (Liber Mineralium II.): "Moreover there is another metal generally unknown called zinken. It is of peculiar nature and origin; many other metals adulterate it. It can be melted, for it is generated from three fluid principles; it is not malleable. Its colour is different from other metals and does not resemble others in its growth. Its ultimate matter (ultima materia) is not to me yet fully known. It admits of no mixture and does not permit of the fabricationes of other metals. It stands alone entirely to itself." We do not believe that this book was published until after Agricola's works. Agricola introduced the following statements into his revised edition of Bermannus (p. 431), published in 1558: "It (a variety of pyrites) is almost the colour of galena, but of entirely different components. From it there is made gold and silver, and a great quantity is dug in Reichenstein, which is in Silesia, as was recently reported to me. Much more is found at Raurici, which they call zincum, which species differs from pyrites, for the latter contains more silver than gold, the former only gold or hardly any silver." In De Natura Fossilium (p. 368): "For this cadmia is put, in the same way as quicksilver, in a suitable vessel so that the heat of the fire will cause it to sublime, and from it is made a black or brown or grey body which the Alchemists call cadmia sublimata. This possesses corrosive properties to the highest degree. Cognate with this cadmia and pyrites is a compound which the Noricans and Rhetians call zincum." We leave it to readers to decide how near this comes to metallic zinc; in any event, he apparently did not recognise his conterfei from the furnaces as the same substance as the zincum from Silesia. The first correlation of these substances was apparently by Lohneys, in 1617, who says (Vom Bergwerk, p. 83-4): "When the people in the smelting works are smelting, there is made under the furnace and in the cracks in the walls among the badly plastered stones, a metal which is called zinc or counterfeht, and when the wall is scraped it falls into a vessel placed to receive it. This metal greatly resembles tin, but it is harder and less malleable.... The Alchemists have a great desire for this zinc or bismuth." That this metal originated from blende or calamine was not recognised until long after, and Libavis (Alchymia, Frankfort, 1606), in describing specimens which came from the East, did not so identify it, this office being performed by Glauber, who says (De Prosperitate Germanias, Amsterdam, 1656): "Zink is a volatile mineral or half-ripe metal when it is extracted from its ore. It is more brilliant than tin and not so fusible or malleable ... it turns (copper) into brass, as does lapis calaminaris, for indeed this stone is nothing but infusible zinc, and this zinc might be called a fusible lapis calaminaris, inasmuch as both of them partake of the same nature.... It sublimates itself up into the cracks of the furnace, whereupon the smelters frequently break it out." The systematic distillation of zinc from calamine was not discovered in Europe until the 18th Century. Henkel is generally accredited with the first statement to that effect. In a contribution published as an Appendix to his other works, of which we have had access only to a French translation (Pyritologie, Paris, 1760, p. 494), he concludes that zinc is a half-metal of which the best ore is calamine, but believes it is always associated with lead, and mentions that an Englishman lately arrived from Bristol had seen it being obtained from calamine in his own country. He further mentions that it can be obtained by heating calamine and lead ore mixed with coal in a thick earthen vessel. The Bristol works were apparently those of John Champion, established about 1740. The art of distillation was probably learned in the East.
Definite information as to the zinc minerals goes back to but a little before the Christian Era, unless we accept nebular references to aurichalcum by the poets, or what is possibly zinc ore in the "earth" mentioned by Aristotle (De Mirabilibus, 62): "Men say that the copper of the Mossynoeci is very brilliant and white, no tin being mixed with it; but there is a kind of earth there which is melted with it." This might quite well be an arsenical mineral. But whether we can accept the poets or Aristotle or the remark of Strabo given above, as sufficient evidence or not, there is no difficulty with the description of cadmia and pompholyx and spodos of Dioscorides (1st Century), parts of which we reproduce in note 26, p. 394. His cadmia is described as rising from the copper furnaces and clinging to the iron bars, but he continues: "Cadmia is also prepared by burning the stone called pyrites, which is found near Mt. Soloi in Cyprus.... Some say that cadmia may also be found in stone quarries, but they are deceived by stones having a resemblance to cadmia." Pompholyx and spodos are evidently furnace calamine. From reading the quotation given on p. 394, there can be no doubt that these materials, natural or artificial, were used to make brass, for he states (V, 46): "White pompholyx is made every time that the artificer in the working and perfecting of the copper sprinkles powdered cadmia upon it to make it more perfect, the soot arising from this ... is pompholyx." Pliny is confused between the mineral cadmia and furnace calamine, and none of his statements are very direct on the subject of brass making. His most pointed statement is (XXXIV, 2): "... Next to Livian (copper) this kind best absorbs cadmia, and is almost as good as aurichalcum for making sesterces and double asses." As stated above, there can be little doubt that the aurichalcum of the Christian Era was brass, and further, we do know of brass sesterces of this period. Other Roman writers of this and later periods refer to earth used with copper for making brass. Apart from these evidences, however, there is the evidence of analyses of coins and objects, the earliest of which appears to be a large brass of the Cassia family of 20 B.C., analyzed by Phillips, who found 17.3% zinc (Records of Mining and Metallurgy, London, 1857, p. 13). Numerous analyses of coins and other objects dating during the following century corroborate the general use of brass. Professor Gowland (Presidential Address, Inst. of Metals, 1912) rightly considers the Romans were the first to make brass, and at about the above period, for there appears to be no certainty of any earlier production. The first adequate technical description of brass making is in about 1200 A.D. being that of Theophilus, who describes (Hendrie's Trans., p. 307) calcining calamina and mixing it with finely divided copper in glowing crucibles. The process was repeated by adding more calamine and copper until the pots were full of molten metal. This method is repeatedly described with minor variations by Biringuccio, Agricola (De Nat. Fos.), and others, down to the 18th Century. For discussion of the zinc minerals see note on p. 112.
Diodorus says (V, 2) regarding tin in Spain: "They dig it up, and melt it down in the same way as they do gold and silver;" and again, speaking of the tin in Britain, he says: "These people make tin, which they dig up with a great deal of care and labour; being rocky, the metal is mixed with earth, out of which they melt the metal, and then refine it." Pliny (XXXIV, 47), in the well-known and much-disputed passage: "Next to be considered are the characteristics of lead, which is of two kinds, black and white. The most valuable is the white; the Greeks called it cassiteros, and there is a fabulous story of its being searched for and carried from the islands of Atlantis in barks covered with hides. Certainly it is obtained in Lusitania and Gallaecia on the surface of the earth from black-coloured sand. It is discovered by its great weight, and it is mixed with small pebbles in the dried beds of torrents. The miners wash these sands, and that which settles they heat in the furnace. It is also found in gold mines, which are called alutiae. A stream of water passing through detaches small black pebbles variegated with white spots, the weight of which is the same as gold. Hence it is that they remain in the baskets of the gold collectors with the gold; afterward, they are separated in a camillum and when melted become white lead."
There is practically no reference to the methods of Cornish tin-working over the whole period of 2,000 years that mining operations were carried on there prior to the Norman occupation. From then until Agricola's time, a period of some four centuries, there are occasional references in Stannary Court proceedings, Charters, and such-like official documents which give little metallurgical insight. From a letter of William de Wrotham, Lord Warden of the Stannaries, in 1198, setting out the regulations for the impost on tin, it is evident that the black tin was smelted once at the mines and that a second smelting or refining was carried out in specified towns under the observation of the Crown Officials. In many other official documents there are repeated references to the right to dig turfs and cut wood for smelting the tin. Under note 8, p. 282, we give some further information on tin concentration, and the relation of Cornish and German tin miners. Biringuccio (1540) gives very little information on tin metallurgy, and we are brought to De Re Metallica for the first clear exposition.
As to the description on these pages it must be remembered that the tin-stone has been already roasted, thus removing some volatile impurities and oxidizing others, as described on page 348. The furnaces and the methods of working the tin, here described, are almost identical with those in use in Saxony to-day. In general, since Agricola's time tin has not seen the mechanical and metallurgical development of the other metals. The comparatively small quantities to be dealt with; the necessity of maintaining a strong reducing atmosphere, and consequently a mild cold blast; and the comparatively low temperature demanded, gave little impetus to other than crude appliances until very modern times.
HISTORICAL NOTE ON IRON SMELTING. The archaeologists' division of the history of racial development into the Stone, Bronze, and Iron Ages, based upon objects found in tumuli, burial places, etc., would on the face of it indicate the prior discovery of copper metallurgy over iron, and it is generally so maintained by those scientists. The metallurgists have not hesitated to protest that while this distinction of "Ages" may serve the archaeologists, and no doubt represents the sequence in which the metal objects are found, yet it by no means follows that this was the order of their discovery or use, but that iron by its rapidity of oxidation has simply not been preserved. The arguments which may be advanced from our side are in the main these. Iron ore is of more frequent occurrence than copper ores, and the necessary reduction of copper oxides (as most surface ores must have been) to fluid metal requires a temperature very much higher than does the reduction of iron oxides to wrought-iron blooms, which do not necessitate fusion. The comparatively greater simplicity of iron metallurgy under primitive conditions is well exemplified by the hill tribes of Northern Nigeria, where in village forges the negroes reduce iron sufficient for their needs, from hematite. Copper alone would not be a very serviceable metal to primitive man, and he early made the advance to bronze; this latter metal requires three metallurgical operations, and presents immeasurably greater difficulties than iron. It is, as Professor Gowland has demonstrated (Presidential Address, Inst. of Metals, London, 1912) quite possible to make bronze from melting stanniferous copper ores, yet such combined occurrence at the surface is rare, and, so far as known, the copper sources from which Asia Minor and Egypt obtained their supply do not contain tin. It seems to us, therefore, that in most cases the separate fusions of different ores and their subsequent re-melting were required to make bronze. The arguments advanced by the archaeologists bear mostly upon the fact that, had iron been known, its superiority would have caused the primitive races to adopt it, and we should not find such an abundance of bronze tools. As to this, it may be said that bronze weapons and tools are plentiful enough in Egyptian, Mycenaean, and early Greek remains, long after iron was demonstrably well known. There has been a good deal pronounced by etymologists on the history of iron and copper, for instance, by Max Mueller, (Lectures on the Science of Language, Vol. II, p. 255, London, 1864), and many others, but the amazing lack of metallurgical knowledge nullifies practically all their conclusions. The oldest Egyptian texts extant, dating 3500 B.C., refer to iron, and there is in the British Museum a piece of iron found in the Pyramid of Kephron (3700 B.C.) under conditions indicating its co-incident origin. There is exhibited also a fragment of oxidized iron lately found by Professor Petrie and placed as of the VI Dynasty (B.C. 3200). Despite this evidence of an early knowledge of iron, there is almost a total absence of Egyptian iron objects for a long period subsequent to that time, which in a measure confirms the view of its disappearance rather than that of ignorance of it. Many writers have assumed that the Ancients must have had some superior art of hardening copper or bronze, because the cutting of the gigantic stonework of the time could not have been done with that alloy as we know it; no such hardening appears among the bronze tools found, and it seems to us that the argument is stronger that the oldest Egyptian stoneworkers employed mostly iron tools, and that these have oxidized out of existence. The reasons for preferring copper alloys to iron for decorative objects were equally strong in ancient times as in the present day, and accounts sufficiently for these articles, and, therefore, iron would be devoted to more humble objects less likely to be preserved. Further, the Egyptians at a later date had some prejudices against iron for sacred purposes, and the media of preservation of most metal objects were not open to iron. We know practically nothing of very early Egyptian metallurgy, but in the time of Thotmes III. (1500 B.C.) bellows were used upon the forge.
Of literary evidences the earliest is in the Shoo King among the Tribute of Yue (2500 B.C.?). Iron is frequently mentioned in the Bible, but it is doubtful if any of the early references apply to steel. There is scarcely a Greek or Latin author who does not mention iron in some connection, and of the earliest, none are so suggestive from a metallurgical point of view as Homer, by whom "laboured" mass (wrought-iron?) is often referred to. As, for instance, in the Odyssey (I., 234) Pallas in the guise of Mentes, says according to Pope:
"Freighted with iron from my native land I steer my voyage to the Brutian strand, To gain by commerce for the laboured mass A just proportion of refulgent brass."
(Brass is modern poetic licence for copper or bronze). Also, in the Odyssey (IX, 465) when Homer describes how Ulysses plunged the stake into Cyclop's eye, we have the first positive evidence of steel, although hard iron mentioned in the Tribute of Yue, above referred to, is sometimes given as steel:
"And as when armourers temper in the ford The keen-edg'd pole-axe, or the shining sword, The red-hot metal hisses in the lake."
No doubt early wrought-iron was made in the same manner as Agricola describes. We are, however, not so clear as to the methods of making steel. Under primitive methods of making wrought-iron it is quite possible to carburize the iron sufficiently to make steel direct from ore. The primitive method of India and Japan was to enclose lumps of wrought-iron in sealed crucibles with charcoal and sawdust, and heat them over a long period. Neither Pliny nor any of the other authors of the period previous to the Christian Era give us much help on steel metallurgy, although certain obscure expressions of Aristotle have been called upon (for instance, St. John V. Day, Prehistoric Use of Iron and Steel, London, 1877, p. 134) to prove its manufacture by immersing wrought-iron in molten cast-iron.
HISTORICAL NOTE ON THE METALLURGY OF ANTIMONY. The Egyptologists have adopted the term "antimony" for certain cosmetics found in Egyptian tombs from a very early period. We have, however, failed to find any reliable analyses which warrant this assumption, and we believe that it is based on the knowledge that antimony was used as a base for eye ointments in Greek and Roman times, and not upon proper chemical investigation. It may be that the ideograph which is interpreted as antimony may really mean that substance, but we only protest that the chemist should have been called in long since. In St. Jerome's translation of the Bible, the cosmetic used by Jezebel (II. Kings IX, 30) and by the lady mentioned by Ezekiel (XXIII, 40), "who didst wash thyself and paintedst thine eyes" is specifically given as stibio. Our modern translation carries no hint of the composition of the cosmetic, and whether some of the Greek or Hebrew MSS. do furnish a basis for such translation we cannot say. The Hebrew term for this mineral was kohl, which subsequently passed into "alcool" and "alkohol" in other languages, and appears in the Spanish Bible in the above passage in Ezekiel as alcoholaste. The term antimonium seems to have been first used in Latin editions of Geber published in the latter part of the 15th Century. In any event, the metal is clearly mentioned by Dioscorides (1st Century), who calls it stimmi, and Pliny, who termed it stibium, and they leave no doubt that it was used as a cosmetic for painting the eyebrows and dilating the eyes. Dioscorides (V, 59) says: "The best stimmi is very brilliant and radiant. When broken it divides into layers with no part earthy or dirty; it is brittle. Some call it stimmi, others platyophthalmon (wide eyed); others larbason, others gynaekeion (feminine).... It is roasted in a ball of dough with charcoal until it becomes a cinder.... It is also roasted by putting it on live charcoal and blowing it. If it is roasted too much it becomes lead." Pliny states (XXXIII, 33 and 34): "In the same mines in which silver is found, properly speaking there is a stone froth. It is white and shining, not transparent; is called stimmi, or stibi, or alabastrum, and larbasis. There are two kinds of it, the male and the female. The most approved is the female, the male being more uneven, rougher, less heavy, not so radiant, and more gritty. The female kind is bright and friable, laminar and not globular. It is astringent and refrigerative, and its principal use is for the eyes.... It is burned in manure in a furnace, is quenched with milk, ground with rain water in a mortar, and while thus turbid it is poured into a copper vessel and purified with nitrum ... above all in roasting it care should be taken that it does not turn to lead." There can be little doubt from Dioscorides' statement of its turning to lead that he had seen the metal antimony, although he thought it a species of lead. Of further interest in connection with the ancient knowledge of the metal is the Chaldean vase made of antimony described by Berthelot (Comptes Rendus, 1887, CIV, 265). It is possible that Agricola knew the metal, although he gives no details as to de-sulphurizing it or for recovering the metal itself. In De Natura Fossilium (p. 181) he makes a statement which would indicate the metal, "Stibium when melted in the crucible and refined has as much right to be regarded as a metal as is accorded to lead by most writers. If when smelted a certain portion be added to tin, a printer's alloy is made from which type is cast that is used by those who print books." Basil Valentine, in his "Triumphal Chariot of Antimony," gives a great deal that is new with regard to this metal, even if we can accredit the work with no earlier origin than its publication--about 1600; it seems possible however, that it was written late in the 15th Century (see Appendix B). He describes the preparation of the metal from the crude ore, both by roasting and reduction from the oxide with argol and saltpetre, and also by fusing with metallic iron. While the first description of these methods is usually attributed to Valentine, it may be pointed out that in the Probierbuechlein (1500) as well as in Agricola the separation of silver from iron by antimony sulphide implies the same reaction, and the separation of silver and gold with antimony sulphide, often attributed to Valentine, is repeatedly set out in the Probierbuechlein and in De Re Metallica. Biringuccio (1540) has nothing of importance to say as to the treatment of antimonial ores, but mentions it as an alloy for bell-metal, which would imply the metal.
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