Author Institution: Department of Chemistry, The Ohio State University, Columbu

Caley, Earle R.

Deebel, Wallace H.

The Ohio Journal of Science

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RESULTS OF AN EXAMINATION OF METAL SPECIMENSFROM AN EXCAVATION OF SHAMSHIR GHAR.AFGHANISTAN1EARLE R. CALEY AND WALLACE H. DEEBELDepartment of Chemistry, The Ohio State University, ColumbusThe specimens discussed in this paper all came from the excavation of thecave site of Shamshir Ghar, Afghanistan, conducted by Dr. Louis Dupree ofHarvard University. This site is situated in the Province of Kandahar, at 31°35' N latitude and 65°30' E longitude, and is about 15 miles WNW of Kandaharcity.According to the findings of Dr. Dupree, this site was not occupied by manuntil after the beginning of the Christian Era. Four cultural levels were iden-tified, all belonging to pre-Mongol invasions.Seven specimens, all more or less corroded, were submitted by Dr. Dupreefor examination. In four of them sufficient metal was present to provide samplesfor quantitative analyses. The descriptions of these specimens and the resultsof our examination now follow.No. 1. Bronze Coin. Diameter =17-18 mm. Weight = 2.37 g. Date =IX-X Cent. A. D. This coin was covered with such a dense and uniform layerof green corrosion products that no trace of a design could be distinguished beforecleaning. After electrolysis, parts of a crude design were visible. For analysisthe surface layers were filed away, and two samples of fairly clean metal wereobtained. The results of the analysis are shown in table 1.These results show that this coin was composed of a lead-tin bronze of ratherhigh lead content. Because of lack of analyses no comparison with respect tocomposition can be made between this coin and other coins of similar provenance.However, it is interesting that bronze of about the same composition was usedfor late Greek coins struck in eastern provinces of the Roman Empire. In allprobability the silver in the alloy was introduced as an accidental impurity inthe lead made from argentiferous galena. Though the proportion of nickel presentas an accidental impurity falls within the normal range for an ancient bronze, theproportion of cobalt is unusually high and may be indicative of copper from aparticular source. There is nothing remarkable about the proportions of ironand zinc. The low summations are due to the presence of undetermined oxygenand other non-metallic impurities present in the form of corrosion products withinthe samples of metal.No. 2. Fragment of Thin Bronze. Length = 25 mm. Width = 15 mm. max-imum. Thickness = ca. 1' mm. Weight = 2.00 g. Date = IX-X Cent. A. D.This appeared to be a segment of a disc, though the complete object could havehad a different shape. Faint traces of an ornamental design were visible on thesurface, which was covered with a thin layer of dirt and corrosion products. Thesewere removed mechanically as far as practicable in preparing the two samplesfor analysis. The results of the analysis are shown in table 2.These results show that this fragment was also composed of a lead-tin bronze,but one of lower tin content and even higher lead content than the metal of thecoin. It is not surprising that the percentages of copper and lead in the twosamples are not in agreement, for in bronze of such high lead content the lead1 Paper presented at the Sixty-fourth Annual Meeting of the Ohio Academy of Science,Delaware, Ohio, April, 1955.THE OHIO JOURNAL OF SCIENCE 55(5): 311, September, 1955.312 EARLE R. CALEY AND WALLACE H. DEEBEL Vol. LVis often irregularly distributed through the alloy. On comparing the figures oftable 2 with those of table 1 it will be seen that both bronzes contained the sameimpurities and that all except nickel were present in higher proportion in themetal of the fragment. The parallelism between the percentages of silver andlead in all samples and the near constancy of the ratios of these percentages,shown in table 3, is a clear indication that the silver was introduced as an impurityTABLE 1Analysis of bronze coinSampleABSampleABCu76.8677.07Sn5.755.78Analysis ofCu/o67.2264.54SnCrf/O3.363.29Pb14.9615.14fragmentPb%25.5328.29Ag0.120.16TABLEof objectAg%0.200.22TableFe0.120.062Ni0.150.11composed ofFe/o0.490.523Ni%0.110.11Ratio of Silver to lead in bronzesCo0.080.C3thin bronzeCo%0.130.12Zn0.200.14Zn%0.660.74Total98.2498 49Total%97.7097.83Pb_ ^14.9615.1425.5328.29Ag%Ag/PbRatio0.120.160.200.220.0080.0110.0080.008along with the lead. The higher proportion of cobalt in the metal of this fragmentas compared to the proportion of nickel is still more indicative of the use of copperore from some particular source. As might have been expected, the summationsof the results in table 2 are low because of the presence of corrosion products inthe samples. In general, the analysis shows that the object from which thisfragment came was composed of a kind of bronze suitable for ornaments but notfor objects requiring hardness or strength.No. 3. Fragment of Pin or Clasp. Length = 32 mm. Weight = 3.84 g.Date = ca. X Cent. A. D. This fragment appeared to be part of the shank ofsome sort of a pin or clasp. Mold marks on its sides indicated that this partof the original object had been formed by casting in a two-piece mold. TheNo. 5 METAL SPECIMENS FROM AFGHANISTAN 313fragment was coated with a thin, rather uniform layer of greyish-white corrosionproducts that contained stannic oxide and basic lead carbonate. The underlyingmetal was soft and white. Preliminary qualitative tests showed the presence oftin and lead as the major components of this metal. For quantitative analysisthe surface layer of corrosion products was filed away, and two samples of ratherclean metal were obtained. However, since the metal of this fragment had under-gone extensive intergranular corrosion, it was not possible to obtain samples freefrom corrosion products. The results of the analysis are shown in table 4.These results show that this fragment was composed of an alloy of tin andlead containing iron and zinc in small proportion as accidental impurities. Thisalloy is a kind of pewter in which the proportion of tin is close to twice that oflead. The closeness of the ratio seems to indicate that the alloy was not theresult of the accidental or careless combination of the two component metals,but was the result of the deliberate combination of carefully measured amounts.No. 4. Broken Piece of Iron Pin or Shaft. Length = 69 mm. Weight = 4.86g. Date = VI I-VI11 Cent. A. D. This was a deeply rusted short length ofstraight rod that still contained some residual metal in its core as shown by testswith a magnet. On removal of the layers of rust mechanically a short, thinpiece of metal was isolated. This iron was so soft that it could be easily filed,SampleABAnalysisSn63.8763.64TABLE• of fragmentPb32.6432.894of pewterZn0.080.07Fe0.030.02Total96.6296.62and so ductile that it could be flattened out easily by hammering. After heatingit to bright redness and plunging it into cold water it still could be easily filedand was still so ductile that it could be hammered out without any sign of fracture.This behavior is characteristic of iron containing a very low proportion of carbon.The metal of this object must have been, therefore, wrought iron or a very mildsteel.No. 5. Broken Piece of Iron Pin or Shaft. Length = 45 mm. Weight = 4.37g. Date = VII-VIII Cent. A. D. This was similar to No. 4 in appearance,though somewhat thicker, and it also contained a short, thin core of metal. Thisiron was noticeably more resistant to the file than the metal of No. 4, and muchless ductile on hammering. After heating it to bright redness and plunging itinto cold water it was still more resistant to the file, and on hammering it brokeinto small pieces. This behavior is characteristic of iron containing enoughcarbon to be classed as a steel. In view of the difference in behavior before andafter heat treatment, it must be concluded that the metal of the object was atempered steel.No. 6. Broken Piece of Iron Arrowhead. Weight = 2.11 g. Date = VII-VIIICent. A. D. This was part of a bayonet-shaped arrowhead with three ribs. Noresidual metal could be detected by means of a magnet. The form of this frag-ment and the extent to which it had rusted clearly seemed to indicate that thearrowhead had been fashioned from either wrought iron or steel but not fromcast iron.314 EARLE R. CALEY AND WALLACE H. DEEBEL Vol. LVNo. 7. Irregular Flat Piece of Cast Iron. Thickness = 3-5 mm. Weight =48.6 g. Date = X-XIII Cent. A. D. This piece of cast iron broke readily onbeing struck with a hammer and showed the bright crystalline structure charac-teristic of white cast iron. It also had the characteristic hardness of this varietyof cast iron, for it could be neither drilled nor filed with tools of ordinary steel.The layer of rust on its surface was not more than a few tenths of a millimeter inthickness, which is not surprising in view of the known resistance of cast iron tocorrosion under natural conditions. This specimen appeared to be a fragmentfrom an iron plate, or possibly a piece from the botton of a dish or pan. Thefact that its thickness tapered regularly from 5 mm. at one end to 3 mm. at theother was perhaps an indication of the latter possibility. One side was smoothand the other slightly rough, which may indicate that the original object wascast in an open mold. A few small blowholes were present in the metal underthe rough surface, and this also may be an indication of the use of this technique.Except for these blowholes the casting was sound. Separate samples were takenfor the determination of the usual constituents of cast iron. The results of thesedeterminations are show in table 5.TABLE 5Analysis of fragment of cast ironC Si P S MnO7 Oi 0/ 0/ 0//o /o /o /o /o4.25 0.13 0.11 trace traceThese results fully confirm the previous observations indicating that this frag-ment was composed of white cast iron. The proportion of carbon is too high forsteel, and is nearly the maximum that can occur in cast iron. Iron containingthis particular proportion of combined carbon is the so-called eutectic alloy ofiron and carbon, the one that melts or solidifies at a lower temperature than anyother combination of iron and carbon. This minimum temperature is 1140°C, atemperature not difficult to reach even in a primitive furnace. The percentagesof the other constituents are much lower than in modern cast iron. Iron of suchhigh purity could have been produced by smelting a carefully selected, pure ironore with charcoal in a blast furnace maintained at a relatively low temperature bythe application of a regulated flow of unheated air. The higher percentages ofimpurities in modern cast iron arise from the use of unselected ore, coke as a fuel,and the higher temperature arising from the use of a blast of preheated air. Fromthe standpoint of quality, the iron in this specimen is superior to modern whitecast iron.GENERAL CONCLUSIONSA surprising variety of alloys and metallurgical techniques are represented bythese few specimens. Such a variety of alloys and skills indicate an advancedstage in the art of metallurgy that could have been reached only on the basis ofa long background of experience and practice.

Results of an Examination of Metal Specimens from an Excavation of Shamshir Ghar, Afghanistan

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Results of an Examination of Metal Specimens from an Excavation of Shamshir Ghar, Afghanistan

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