An International Journal of MINERALOGY, CRYSTALLOGRAPHY, GEOCHEMISTRY, ORE DEPOSITS, PETROLOGY, VOLCANOLOGY and applied topics on Environment, Archaeometry and Cultural Heritage DOI: 10.2451/2012PM0021 Periodico di Mineralogia (2012), 81, 3, 359-377 perIoDICo di MInerAlogIA established in 1930 Periodico di Mineralogia (2012), 81, 3, 359- Mineralogical and chemical investigations on the ceramic technology in Čoġā Zanbil, (Iran, 1250 B.C.) Mohammadamin Emami 1,* and Reinhard Trettin 2 1 Faculty of Conservation, Art University of Isfahan, P.O. Box 1744, Isfahan, Iran 2 Institute for building- and materials chemistry, University of Siegen, Paul Bonatz Str. 9-11, D-57068 Siegen, Germany * Corresponding author: [email protected]Abstract Characterizations of archaeological finds are an essential feature for the interpretation of data from excavations. The investigated samples date from Elam period (1250 B.C.), which is an important period for archaeology, because of the introduction of new technologies that ameliorate the quality of materials used in daily life, and furthermore because of the expansion of the Elamite kingdom in the Iranian plateau. Basically this paper focused on the investigation of the parameters which have been interested for characterizing the ceramics production in the past. The ceramic pieces studied in this paper come from archaeological excavations carried out in Čoġā Zanbil, in the south west of Iran, between 2002 and 2004. Based on archaeological interpretation they belong to the middle Elamite period (1500-1100 B.C.). The samples have been investigated by quantitative X-ray diffraction inclusive Rietveld phase refining method for determining the crystalline phases in the matrix of ceramics, and simultaneous thermo analysis to characterize the decomposition of the constituent phases during the sintering process. Furthermore thermo analytical studies proved that, during the middle Elamite period, existed a dissimilar thermal behaviour due to different fabrication conditions. Observation by polarized light microscopy included additional information on the manufacturing process by means of the identification of different additives, used within the ceramic matrix. The results provided information on the existence of a similar raw material, and different manufacturing technique in the ceramic production in the middle Elamite period, in Čoġā Zanbil. Key words: Archaeometry; Ceramic; Powder Diffraction; Rietveld Method; Simulated Thermo Analysis; Polarized Light Microscopy; Elamites; Čoġā Zanbil; Iran.
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An International Journal ofMINERALOGY, CRYSTALLOGRAPHY, GEOCHEMISTRY,ORE DEPOSITS, PETROLOGY, VOLCANOLOGYand applied topics on Environment, Archaeometry and Cultural Heritage
DOI: 10.2451/2012PM0021Periodico di Mineralogia (2012), 81, 3, 359-377
perIodICo di MInerAlogIAestablished in 1930
Periodico di Mineralogia (2012), 81, 3, 359-
Mineralogical and chemical investigations on the ceramic technologyin Čoġā Zanbil, (Iran, 1250 B.C.)
Mohammadamin Emami1,* and Reinhard Trettin2
1Faculty of Conservation, Art University of Isfahan, P.O. Box 1744, Isfahan, Iran2Institute for building- and materials chemistry, University of Siegen,
Paul Bonatz Str. 9-11, D-57068 Siegen, Germany*Corresponding author: [email protected]
Abstract
Characterizations of archaeological finds are an essential feature for the interpretation ofdata from excavations. The investigated samples date from Elam period (1250 B.C.), whichis an important period for archaeology, because of the introduction of new technologies thatameliorate the quality of materials used in daily life, and furthermore because of the expansionof the Elamite kingdom in the Iranian plateau.
Basically this paper focused on the investigation of the parameters which have beeninterested for characterizing the ceramics production in the past.
The ceramic pieces studied in this paper come from archaeological excavations carried outin Čoġā Zanbil, in the south west of Iran, between 2002 and 2004. Based on archaeologicalinterpretation they belong to the middle Elamite period (1500-1100 B.C.).
The samples have been investigated by quantitative X-ray diffraction inclusive Rietveldphase refining method for determining the crystalline phases in the matrix of ceramics, andsimultaneous thermo analysis to characterize the decomposition of the constituent phasesduring the sintering process. Furthermore thermo analytical studies proved that, during themiddle Elamite period, existed a dissimilar thermal behaviour due to different fabricationconditions. Observation by polarized light microscopy included additional information on themanufacturing process by means of the identification of different additives, used within theceramic matrix.
The results provided information on the existence of a similar raw material, and differentmanufacturing technique in the ceramic production in the middle Elamite period, in ČoġāZanbil.
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Introduction
The southwest of Iran - an area not far fromthe domains of the Zagros Mountains, betweentwo large rivers named Karoon and Dez - is thebirth place of the great kingdom of Elam in ca.4000 B.C. (Potts, 1999). This region is locatedin ca. 90 km north of the city Ahvaz and 35 kmsouth of the ancient city of Susa (Figure 1). Inthe mid-14th century, the southern district of theSusiana plain was elected as capital of Elam byking “Untsh Gal”. He ordered to build a holycapital called “Dor Untash” as a pilgrimagecentre. Today, this holy city is known as ČoġāZanbil (Figure 2), and is located 25 km from theresidential place, Haft Tappeh (Ghirshman, 1968,Negahban, 1991). Čoġā Zanbil is an importantarchaeological site in the Susiana plain and it isdated to the Elamite period due to thearchaeological finds. The archaeologicaldocumentation on this area goes back to reports,written in 1962 by R. McCormik Adams.Excavations in Čoġā Zanbil and in the peripheryof the city began in autumn 1966, and weredirected by Grishman (1968).
According to the archaeological interpretationsbased on the stylistic features of finds such asceramics and architectural foundations, theElamite period is divided into four sub-periods(Potts, 1999):
(I) Proto- Elamite (4000 - 2500 B.C.) (II) Early Elamite (2500 - 1500 B.C.)(III) Middle Elamite (1500 - 1100 B.C.) (IV) The recent Empire (750 - 640 B.C.)
Čoġā Zanbil is not only important as thereligious periphery of the Elam dynasty, but inthe ancient world it was also a technical centrefor the production of bronze objects, as well asof binding material, ceramics and bricks(Emami, 1996; Emami et al., 2008; Oudbashiand Emami, 2010). According to archaeologicalevidence and geological settings in the region,the settlements had once great potentialities in
the use of soil and natural resources in thevicinity, where they could gather the best qualityminerals. Clay, calcareous stone, gypsum andgranite outcrops are among the most importantnatural resources that would also contribute toagricultural activities in this part of the Susianaplain. The soft bituminous stones were really agift for the civilian of Susiana and Mesopotamia(Le Chatelier, 1912). The data suggest that therivers were the most important paths fortransferring technology and trading science(Sumner, 1972).
Ancient ceramic artefacts are among the mostinteresting objects to study the relationshipbetween man and environment. Indeed, everypiece of pottery is an open book on itsmanufacturing process and on its history(Maggetti and Schwab, 1982). The objects whichare being investigated here, can be distinguishedby their differences in shape and colour as wellas in their matrix. Based on the archaeologicalobservation and reports carried out in this field,pottery is the most commonly found everydayproduct, often catalogued in enormous quantity.Archaeological investigations have been carriedout for some years, but the analytical evaluationsof archaeological finds from this area are a recentinvestigation.
Ancient pottery is described as an object witha high porosity and a clayey matrix with eitherdifferent or similar kinds of mixtures with aglassy matrix (Salmang and Scholze, 1983). Foran archaeometrically oriented mineralogist,pottery is manufactured by means of differentpyrotechnological processes. The mostinteresting questions are: how long does thecraftsman or potter use the same manufacturingprocess or similar raw materials? If there wasany challenge, which kind of technical highlightscan be identified by investigations?
For this study different analytical approacheshave been used for the characterization ofceramics from Čoġā Zanbil (1500-1100 B.C.).Classifying ceramics involves the understanding
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of the different manufacturing process, usedduring a well-known historical period withrespect to their raw materials and manufacturingprocesses. After the characterization of ceramic,the study of the manufacture and theperformance of ceramics residues, the focus isnow on the development of manufacturingtechniques of pottery dated to the time between1250 and 700 B.C., discovered in theexcavations in 2004.
The ceramic remains considered here showeddifferent shapes and style as well as differentphysical and chemical properties, depending ontheir structure and constituent minerals, expectedin some investigated ancient ware fromMesopotamia (Noll, 1990). Models for theinvestigation on potteries have for a long timebeen focussed on research carried out bydifferent authors (Emami and Trettin, 2010). The
archaeological evidence on Čoġā Zanbil ispublished in various reports, but these may inpart reflect theoretical concepts that do not matchlaboratory results. In this paper the results ofscientific analysis of ceramic remains areoutlined.
Application of quantitative x-ray diffractionwith Rietveld refining method and themo-analysis have discussed on the ceramics fromPersepolis, Iran (Emami et al., 2011). Thesemodels take into account the differentmethodological path in the resource-rich ofancient civilizations (Maggetti et al., 2011). Inthis paper, the beginnings of the production ofceramics in south west of Iran will be puttogether with a cursory overview of thecharacterization of ceramic pieces. Bysynthesizing data from a number of currentresearch projects, exploring the usage of
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Figure 1. Map showing the location of sites and nearby roads and cities.
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mineralogical data for interpreting of ancientobjects (Drebushchak et al., 2011; Szilagyi et al.,2012).
Geological settingThe geological setting is important for
understanding the geological- and mineralogicaldevelopment of the earth through time.Morphological and geological features in thisregion demonstrate it to be a field with typicalcomplex structures including geosynclinals andnew marine sedimentation in the south west ofIran, close to the Iraqi border. This setting causedessential occurrences on the raw materialsthrough out of geological process, and theiroutcrops on the earth, in different facies (Tehrani,1989). Erosion can be seen all around theKhuzestan province and occurs in differentformations on the ground. River streams,underground irrigation, hot and dry weather,thaw-freezing effects and salt recrystallizationare the main effects causing corrosion in theKhouzestan province and mainly around theČoġā Zanbil complex (Bullard, 1970).
The Iranian plateau is affiliated with theupduction of Former Ocean Tethys in 190million years ago and, accordingly, it is expectedto have mainly outcrops consist of biochemicaland marine carbonate sediments (Van der Voo,
1993). There are three important formationswhich are responsible for the geological settingof this area: The Agha-Jari formation, theLahbari formation and the Quaternary formation.The entire sedimentary sequences are illustratedin Table 1.
Agha-jari consists of red-grey sandstone andgreywacke, and the chemical variation dependsfrom the Fe3+/Al3+ ratios in its sandstone. Suchmelange outcrops are interpreted as highsubduction erosion on the surface (Gradstein etal., 2004). The Agha-Jari formation consists ofgypsum and mergel which became visible incalcareous formation as well as chertarnite. Thesedimentation facies, classified from early timeto the recent period, include (I) mergel sand stone(M-Plams), (II) Conglomerate (M-Plac) and (III)recent sandstone with conglomerate (M-Plasc).
The Lahbari formation consist mainly of calc-arnite, limestone, silt and fine granular sandstone,followed by a thin layer of gypsum and mergel,above which there is alluvial sedimentation(Fesharaki et al., 2007). The Lahbari formation isclassified by two sub layers on this field: (I) earlyLahbari (Pl1la) and (II) recent Lahbari (pl2la).
The quaternary formation outcrops arecommon on this field and surrounded ČoġāZanbil, but were very rapidly eroded. Themineralogical sequences contain silt, sand and
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Figure 2. Temple of Čoġā Zanbil built by Untash Gal in 1250 B.C.
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clay. This setting is also responsible for a clayeyreservoir on the field. The Quaternary containsfive sublayers; (I) old tercier (Qt1), (II) jungtercier (Qt2), (III) weathered layer (Q5), (IV)recent tercier (Qt3) and (V) recent alluvialsediments (Qt4 - Qal). The lithological data provedthat in this sequence conglomerates consist ofgranular quartz sandstone, cemented with acalcareous matrix. Granular sandstones are notwell rounded due to their nearness to the originalsources.
Recently alluvial sedimentation is mainlyobserved near the temple and it is forming tilltoday (Malek-Abbasi, 2004). Saltrecrystallization and salt pillars densenessaround Čoġā Zanbil suggest typical marineevaporate on the field that followed bymetamorphose. In the external part of the soilcloride enrichment as MgCl2 compositionappeared in some accumulation texture on thefield. High carbonate enrichment is caused byevaporation of seawater. The formation in a thinlayer consists of gypsum. Anhydrite was
expected, because of the evaporation ofcarbonate in an arid climate with sulphateconstituents.
The best sedimentation sequences are observedin the water canals close to the temple. Accordingto the strata formation, the Qt4 and Qal are both themain sediments around Čoġā Zanbil. These twosequences have the same old standing butdifferent lithological-mineralogical constituents.
Material and Methods
Samples DescriptionThirty five samples (ceramic pieces) from
surface excavation as well as archaeologicalexcavation have been selected, with specialattention to their morphology, surface characterand textural property. The objects are supposed tohave been produced in Čoġā Zanbil and they weresampled because of the reasonable attribution tothis field. The samples have been archaeologicallyand iconographically studied, and because of theirstylistic features their provenance from Čoġā
Table 1. Related geological time scale on the field.
Period Symbol
Qal New alluvial sediments consist of sand, silt and gravel .
Q14 Alluvial sediments with sand silt and clay with the remains of corroded material from the building.
Q13 Accumulation of new alluvial sediments consists of fain stone agglomerate, sand and gypsum.
Qla Secondary sedimentation of gypsum and sand.
Q12 Accumulation of new compact sediments wich consists of granular stone aggregates.
Q11 Old standing alluvial sediments consist of conglomerates and granular sand.
PL2la Recently weathering consists of sand, conglomerate and clay.
PL1la Exchangeable layers between gypsum and sand.
M-PLG Sedimentation of greyish sand and clay with gypsum.
Qua
tern
ary
Hol
ocen
e
Terti
ary
Neo
gene
Mio
pala
eoge
ne
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Zanbil has been accepted (Mofidi Nasrabadi,2003). The investigated samples are mainly datedto the middle Elamite period (15th B.C.) and showa great variety with respect to their functionality.The ceramics are mostly vases, bowls, jugs andplates.
Chronologically, the ceramics dated to 250 BCare the earliest found in Čoġā Zanbil. The shapesof these objects are mostly similar, but their colorvaries considerably from white (8/2) to bright olive-green (6/3) to reddish-yellow (6/8) yellow (8/6) andpink (7/4), based on the Munsell table of color. Theeffect of straw (organic additives which have beenused to clayey raw materials) can also be observedon the surface. The ceramic pieces have beenselected as relevant samples, belonging to the samerange of dating (1500 to 1100 B.C.) (MofidiNasrabadi, 2003; Malek-Abbasi, 2004).Classification of the samples according to theirapplications and their related dating are describedin the Table 2. To get a good overview to thesamples, macroscopical illustrations of some piecesare shown in the Figure 3.
Analytical Methods The investigation of the ceramic samples has
been carried out by following some criteria thatmust be taken into account in the interpretationand characterization of samples:
(I) the consistency of the matrix for theinterpretation of mechanical properties of ceramicmatrices (Wong and Buenfeld, 2006);
(II) the characterization of the binding materialby means of clayey-, calcareous- and organicbased materials, that was also recognized as partof the matrix as fine-, crude and colloidal matrix(Maggetti and Schwab, 1982);
(III) the characterization of the mineralogicalconstituents for interpreting the raw materialprocessing as well as the development of the firingtechnology and the surface modification of ancientproducts (Martineau et al., 2007, Emami et al.,2008).
Chemical composition of ceramics in the(CaO+MgO) - SiO2 - Al2O3 system
The result of the XRF analysis on the ternarysystem (CaO+MgO) - SiO2 - Al2O3 proved thatthe pottery from Čoġā Zanbil has to be classifiedas calcium rich, till high calcium-rich ceramic(Noll, 1991; Emami, 2008) (Figure 4, Table 3).According to the (CM)SA diagram the resultsconcentrated in the quartz - diopside - anorthiteline, based on the usage of mostly calcareous raw
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materials. The distribution of the results of bulkchemical analysis in this area illustrate that theresults are not clustered in a separated areas, butalso that they are scattering toward the quartz –calcite line, interpreted as essential for choosingthe raw materials from 1200 till 700 B.C.
(Emami et al., 2008). The distribution indicatesthat the raw materials seem to be dissimilar inthe passing of time. As shown by the calciumconstituent from calcareous materials in thesamples, the objects from Čoġā Zanbil are moreor less analogous to the ceramics from other
Table 2. Classification and description of samples according to their applications.
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parts of Mesopotamia (Noll, 1991). Calcium-richceramics are used for decorative features becauseof their bright surface and allow of surfacemodifications for aesthetic purposes. Thecharacter of the surface in calcium-rich ceramicsincreases the workability of the object, and it isemployed for a better quality of surfacedecoration. Geological surveys in this areaidentified near Čoġā Zanbil alluvial soil setting,consisting mainly of calcareous material (Malek-Abbasi, 2004). The manufacturing processcontinued as a kind of non-continuous tradeduring the middle Elamite period.
Quantitative X-Ray Diffraction by RietveldRefining Method
Phase determinations of pottery have beencarried out by QXRD. The major crystallinephases in the matrix are calcite, quartz, feldspars,plagioclase and also high temperature phasessuch as pyroxene. The preferred orientations ofcommon crystalline phases are shown in Figure5. Quartz shows coarse grain aggregate, and ismostly used as admixture. The aggregates arewell crystallized and the preferred orientationcomes at 2θ=26°. Quartz become noticeable ascrushed granite fragments and shows a different
Figure 3. Some analysed samples with the number of the ceramic pieces.
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morphology as siliceous-igneous sources orclastic sedimentary rocks with influences ofmetamorphoses on their crystal structure,illustrated as typical undulatory extinction(Monnin et al., 2006). Granite fragments occurnormally with alkali-feldspar, plagioclase, biotiteand muscovite (Figure 6). Quartz shows a mostlyrounded shape as result of the long transportationpath from its original place. In general, in thesegroups the admixtures vary between crushedgranite and sedimentary fragments. The variationof admixtures in the ceramic structuredemonstrates that pottery makers would workwith different materials to achieve a betterquality production.
Calcite and iron oxide are used as flux orappear, after the firing process, as secondary
Figure 4. Bulk chemical composition of pottery withrespect to calcium-silica constituents in the ternarysystem CaO+MgO-SiO2-Al2O3 in wt%.
Figure 5. Diffractogram of one of the ceramics analyzed by XRD and refined by Rietveld calculation.Quartz- ICSD 79634, Calcite- ICSD 40544, Anorthite- ICSD 34942, Orthoclase- ICSD 34742, Albite- ICSD87655, Microcline- ICSD 100495, Augite- ICSD 56921, Diopside- ICSD 64977, Muscovite- ICSD 202263,Dolomite- ICSD 40971, Illite- ICSD 55333, Gehlenite- ICSD 20392, Analcime- ICSD 87555.
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crystallized phases in the matrix (Figure 7). Theamount of Mg-rich carbonate proves that alsodolomite is a common carbonate used as rawmaterial. The enrichments of magnesium incarbonate - as dolomitic composition - can alsobe detected under polarized microscopy throughthe red rim remaining around calcium carbonate,responsible for the accumulation of periclase dueto decomposition of dolomite: CaMg(CO3)2→CaO + MgO + CO2↑ by approximately 870 °C(Figure 7). In this condition one hypothesis saysthat periclase diffuses from the dolomite or highmagnesium calcium carbonate, and some of itremains as red relic around the aggregate orporosity in the matrix. Alternatively, it could bea pore with secondary calcite formation.Gehlenite and pyroxene is mainly the reactionproduct from clayey raw material. Diopsideoccurs in Mg-rich matrix, rebuilt under hightemperature conditions.
Because of the inhomogeneity of the ceramicconstituents, all atomic and symmetry parametershave been refined through the Rietveld method toget a better matching in the structure of thecalculated phases. Furthermore, all refineddiffractograms have been compared to each other
to gain a better understanding of the crystallinephase constituents (Figure 8). The refining ofsome phases is difficult as they occur as very finecrystals, such as analcime (trigonal-rhombohedral), detected before quartz andoverlapped with the best preferred orientation ofquartz. Before the best peaks of quartz in 2θ=26°,Analcime (Na[AlSi2O6]·H2O) appeared based onweathering of albite and absence of 1 mole SiO2in its crystal structure in humid environment,accordingly (Deer et al., 1992). The qualitativephase investigation in this period proves thatmuscovite contains 1.4 wt% of the ceramictexture. Muscovite occurs with its best intensityon the plane (025) and its best preferredorientation at 2θ=13.5°. Muscovite is mostlyoverlapped by the major picks of quartz anddiopside. Another imperative paragenesis in thepottery is due to the presence of the mineralscarrying calcium and magnesium. Calcite, augite,diopside and gehlenite are the typical mineral inthis group and the occurrences of the phases in aceramic are dependent on the firing temperature,cooling rates and atmosphere of kiln (ƒCO2)(Matson, 1971). The ceramics can bedistinguished and sorted according to the
Figure 7. Diffusion and accumulation of periclase asrelict of red rim on the external layer of carbonate afterthe dissolution of the dolomitic constituents.
Figure 6. Granite fragments as quartz assembling withundolatory extinction. Quartz grain are cemented in aclay/calcareous matrix and form a very compactquartz mosaic
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occurrence of Ca/Mg silicate. Consequently thegehlenite/pyroxene ratio has a great variationdepending on the different soil, in which it isburied for a long time. The composition ofplagioclases and feldspars varies with respect tothe raw materials used in the manufacture. XRDanalysis proved that the samples contain highamount of anorthite and K-feldspars (4.5 wt%)originating from the clay. The alteration processesof K-feldspars confirm that potteries from ČoġāZanbil are made from an illite reservoir.
Phase decomposition by Simultaneous ThermoAnalysis (STA)
The results based on STA-Analysis proved thatthe temperature reach approximately 1191 °C(Figure 9, Table 4). At this temperature, prolongfiring goes to intensive smelting process due tothe partial smelting between the surfaces of
constituents clay grains (Traore et al., 2000;Rathossi et al., 2010). According to occurrencesof hematite due to the oxidation of iron (II) toiron (III), it can be determined that the firingprocess has been carried out under oxidationconditions. The decomposition of carbonates (by720-870 °C) is a reason for a differentatmospheric condition in the kiln with respect toƒCO2 (Emami et al., 2009). ƒCO2 increasedbecause of the decomposition of calcite (CaCO3 ↔ CaO + CO2↑). For a very shortmoment ƒCO2 increased in the kiln atmosphereand the reaction go to the left side. As a result,secondary calcites are produced in the porosity.This effect was enhanced through the influenceof CO2 partial pressure on the kiln atmosphereas a closed system. The firing process hastherefore been carried out in a short time inreduction conditions. The shifting of the
Figure 8. QXRD diffractograms refined by Rietveld method from Čoġā Zanbil (12th B.C.).
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decarbonatization peak demonstrates that theatmospheric swap was controlled by CO2 partialpressure in the kiln. After the STA-diagram anddehydration scope, the firing temperature ismainly constant and in this period the raw
material might have been illite rich clay.Gehlenite is expected to have been crystallized
in higher amount than clinopyroxene in low firedlamps (ca. 800 °C) (Traore et al., 2000). In lampsfired at temperature higher than 1000 °C or for
Table 4. Mineral decomposition of the ceramics due to their temperature increasing in the kiln.
< 200 °C Physical bonding water vanish
DSC Value 400-600 °C Decomposition of kaolinite to metakaolinite Al2(OH)4(Si2O5) → Al2O3·2SiO2 + 2H2O
DSC Value 734-852 °C Oxidation of impurities as well as decarbonisation DSC Value 780-1000 °C Emerging of spinels 2(Al2O3·2SiO2) → 2Al3O3·3SiO2+SiO2, additionaly Gehlenite and Pyroxene rebuilt in this area Secondary Iron oxide appeared
DSC Value 1000-1150 °C Crystallization of spinelle from metakaolinite and emerge of Mullite 3Al2O3 + 6SiO2 → 3Al2O3·2SiO2 + 4SiO2
TG Mass Exchange -4,5% (589-760 °C)
Figure 9. STA Diagram of the ceramics from 12th B.C. from Čoġā Zanbil.
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prolonged retention at the maximumtemperature, the gelhenite content is expected tohave been diminished as it is reacted withresidual quartz towards anorthite andwollastonite (Rathossi et al., 2010), and thereforesome high temperature phases are overlappedeach other in XRD diagrams.
Mineralogical and petrological observationsThe Matrix. The matrix of the objects might beclassified based on grain size, fractionalproperties and porosity distribution in thesamples (Emami and Trettin, 2010). The matrix colour goes from green to brightgreen, because of chlorite, clinochlore and mainlydiopside incidences. The matrix of the samples iscompact and the porosity is reduced accordingly.The porosity in these structures is mainlysecondary since they extended after firing. Thedifference between the textures of the ceramicscan be discussed on the basis of occurrences ofquartz – alkali feldspar – (± plagioclase) and mica.Iron and iron-components are mainly observed inthe porosity of ceramics and they mostly cause thecommonly observed red color of such objects(Maniatis and Tite, 1981). The occurrence of ironminerals such as hematite (Fe2O3) and goethite(FeOOH) proves that the iron rich phases generatethrough accumulation of colloidal iron richcomponents coming from the clayey resources.The accumulation of iron phases as hematiteproves that the firing temperatures passed througha high oxidation reaction, as consequentlyhematite appear together with magnetite at a lowertemperature (Pownceby and Clout, 2000). Therecrystallization of hematite is also a reason for ahigh temperature reaction (Emami and Trettin,2010).
Mineralogical constituentsPetrological observations and investigationsshow that the objects consist of aggregates ofgranite and coarse grain sedimentary stone. Bothconsist of calcareous materials. In this group,
calcite is used as an admixture in the texture ofceramics and occurs either as primary or assecondary calcite. Furthermore, observationsprove that the raw materials vary betweencalcitic and dolomitic compositions. Accordingto the high constituents of calcareous andsiliceous materials, an invariant reaction takesplace, and leads to a heterogeneous materialconsisting of quartz and calcite, rebuilding aglassy and a pyroxene rich matrix. Increasing theCa-containing minerals will increase thevariation of pyroxenes, such as wollastonite,augite and diopside, in the matrix (Equation 1and 2). The stability of such minerals depends onthe alkali oxide/SiO2 ratio. Pyroxene couldtherefore be a thermometer for the wholesintering reaction.
Equation 1
Equation 2
Plagioclases are the most common minerals inthe matrix, and form tiny crystals approximately50 µm to 1 mm in length. These aggregates aremostly prismatic with hypidiomorph toxenomorph morphology and they also growalong the (010) surface. They occur as post-deformation rebuilt crystals in the matrix from800 °C. Plagioclases proved alteration effects ontheir surface as sericitization which proved theweathering condition in which the graniticresource was located (Figure 10). Alkalifeldspars appeared mostly through exsolution ofNa-lamellas on the orthoclase (optically ismicrocline) as reason for magmatic resource of
CaCO3
Calcite
SiO2Quartz
~ 750 CCaSiO3
Wollastonite
CO2
(Ca, Mg)SiO3
Augite / Diopside
CO2
CaMg(CO3)2Dolomite
SiO2Quartz
~850 C
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additions to the ceramic (Figure 11).Biotite and muscovite are detectable through
microscopic observations. Biotite originatesfrom clayey raw materials as well as fromcorroded sediments. They can be detectedthrough their red-brown color due to Fe2+/Mg2+
to OH, their typical cleavage perpendicular to{001} surface and also their pleochroitic effect.Biotite decomposes through the firing processaccording to the dehydration reaction by 790 -840 °C (Eq. 3); this reaction causes the formationof pertithic structure in biotite (Okrusch andMatthes, 2006).
Equation 3
The existence of diopside and alkali feldsparsin the matrix leads to estimate the firingtemperature to around 950 °C < T < 1100 °C,then the alkali feldspars are molten by highertemperatures. According to the mineralogicalsystem NaAlSi3O8 - KalSi3O8 - SiO2 it seemsthat the stability area stands in the feldspar -
tridymite area and therefore the sintertemperature must not be higher than 1100 °C.
Concluding remarks
Mineralogical-chemical investigations onceramics from Čoġā Zanbil (12th B.C.) allowuseful interpretations regarding the manufactureof pottery in this area. Based on petrographicalobservations, the materials used for pottering inČoġā Zanbil seem to have sedimentary originswith some metamorphic influences.
The chemical composition and the calculatedcrystalline phase constituents in the body ofceramics are in the system SiO2 - Al2O3 -(CaO+Na2O+K2O) - (MgO+ƩFexOy) (Figure12). The segregated part from the tetrahedraldiagram shows CaO-rich materials as calcareousraw material used in the ceramic production.K2O and CaO as flux are among them, and thesinter temperatures, based on the stability fieldof these phases, decreased. The prolongtemperature reaction also caused thecrystallization of pseudo-mullite as a reason forpartial smelting at temperature between 1000 to1100 °C. The common minerals paragenesisshowed as follow:
1) Anorthite - Calcite - Diopside
Periodico di Mineralogia (2012), 81, 3, 359-377374 Emami and Trettin
Figure 10. Sericitization on plagioclase as a result ofweathering reactions.
Figure 11. Na-lamellas as exsolution relicts onorthoclase.
2KMg3AlSi3O10(OH)2Biotite
! " # # # # $ # # # # + 6SiO2
Quartz! " $ " 3Mg2Si2O6
Orthopyroxene! " # $ # !
+ 2KAlSi3O8
Kalifeldspars! " # $ # + Water !
Emami et Trettin_periodico 19/12/12 14:33 Pagina 374
Mineralogical- chemical investigations on the ... 375
2) Gehlenite - Augite - Diopside - Ca-plagioclase
3) Anorthite – Diopside Clustering of phase constituents (by QXRD)
shows that the technology used here varieddepending on the raw material and theadmixtures. The matrix consists of iron-rich clay,well processed and manufactured underoxidation reaction. The pottery technology in thisarea shows a few changes and the technologyremained constant. The atmosphere of the kilnchanged because of the shifting of the calcitedecomposition peak range and therecrystallization peaks by 800 °C to 900 °C. Thenew crystallization of wollastonite, diopside andanorthite through residual quartz allow thesupposition that the sinter took place under1000 °C (ca 950 °C ), but due to the absence ofhigh temperature phases such as mullite, thereaction continues as partial smelting instead of
firing. Different ceramic processing was carriedout in Čoġā Zanbil with dissimilar firingconditions, with similar raw materials andadmixtures as filler in the pottery. Firing processdivided in two groups: sintered ceramics andintensive smelted ceramics
Acknowledgements
The authors gratefully acknowledges Dr. R.Martineau, scientist at CNRS, and an anonymousreferee for kindly proof reading this article andindicate important highlights to accomplish this paper.
references
Adams R.M. (1962) - Agriculture and urban life inearly southwestern Iran. Science, 136, 109-122
Bullard R. G. (1970) - Geological Studies in FieldArchaeology. Biblical Archaeologist, 33, 98-132.
Deer W.A., Howie R.A. and Zusmann J. (1992) - An
Periodico di Mineralogia (2012), 81, 3, 359-377
Figure 12. Mineral paragenesis in the ceramics from Čoġā Zanbil in tetrahedral diagram SiO2 - Al2O3 -(CaO+Na2O+K2O) - (MgO+ƩFexOy).
Emami et Trettin_periodico 19/12/12 14:33 Pagina 375
Emami and Trettin376
introduction to the rock-forming mineral, 3rd
Edition, Longman Scientific & Technical.Drebushchak V.A., Mylnikova L.N. and Drebushchak
T.N. (2011) - The mass-loss diagram for the ancientceramics. Journal of Thermal Analysis andCalorimetry, 104, 459-466.
Emami M. A. (1996) - Relation of Geological Surveyswith Pathology of Historical Materials and Ambits(Geoarcheology of Choghazanbil Temple).Proceedings of 1th Symposium on Reservation andRestoration of Historical- Cultural Heritages (455-465). Tehran: Research Center of Conservation andRestoration of Cultural Heritage.
Emami M.A. (2008) - “Mineralogisch chemischeUntersuchungen zur Archaeometrie elamischerKeramiken aus Khousestan, Iran”, Dissertation,Universitaet Siegen, URN: nbn: hbz: 467-3603
Emami M. A. and Trettin R. (2010) - Phase generatingprocesses in ancient ceramic matrices throughmicrostructure investigation with high resolutionmicroscopy methods. Journal of AdvancedMicroscopy Research, 5(11), 181-189.
Emami M., Kowald, T. and Trettin R. (2009) -Mineralogical and chemical investigation on therecrystallization process during sintering in face-interface areas in ancient ceramic matrices.Materials and Manufacturing Process, 24, 934-941.
Emami M., Volkmar J., and Trettin R. (2008) -Quantitative characterization of damagemechanisms in ancient ceramic by quantitative X-ray powder diffraction, polarization microscopy,confocal laser scanning microscopy and non-contact mode atomic force microscopy. SurfaceEnginnering, 24, 129-137.
Emami M., Volkmar J. and Trettin R. (2011) -Characterization of Ancient Ceramic Matrices withHigh Resolution Microscopy Methods, LaserScanning, Theory and Applications, Prof. Chau-Chang Wang (Ed.), ISBN: 978-953-307-205-0,InTech.
Fesharaki O., García-Romero E. Cuevas-González J.and López-Martínez N. (2007) - Clay mineralgenesis and chemical evolution in the Miocenesediments of Somosaguas, Madrid Basin, Spain.Clay Minerals, 42(2), 187-201.
Gasparik T. (1990) - A thermodynamic model for theenstatite-diopside join. American Mineralogist , 75,1080-1091.
Ghirshman R. (1968) - Tchoga Zanbil (Dur Untash),
Vol. II. Temenos, temples, palais, tombes. Paris:Memories de la delegation archaeologique en Iran40.
Gradstein F.M., Ogg J.G. and Smith A.G. (2004) - AGeologic Time Scale. Cambridge University Press,and the official website of the InternationalCommission on Stratigraphy (ICS) underwww.stratigraphy.org.
Heimann R. B. (1978) - Mineralogische Vorgaenge beimBrennen von Keramik und Aechaeothermometrie.Acta Prehistorica et archaeologica, 9, 10, 79-101.
Kambakhsh Fard S. O. (2001) - Pottery in Iran, fromNeilithic Period to the Present. Tehran, Iran:Qoqnoos Publishing.
LeChatelier H. (1912) - Note sur la matiere noire etbitumineuse de certains reliefs et statuettes.Mermories de la delegation en Perse XIII , pp. 162.
Louër D., and Louër M. (1972) - Méthode d’essais eterreurs pour l’indexation automatique desdiagrammes des poudre. Journal of AppliedCrystallography, 5, 271-275.
Magetti M., and Gelatti G. (1982) - Dierefernzgroupe(n) Lousana-mineralogische undchemische Untersuchungen der keramischenProduktion der Toepferwerkstaette Berna.Jahresbericht der schweizerichen Gesellschaft fuerUr- und Fruehgeschichte, 65, 109-132.
Maggetti M., and Schwab H. (1982) - Iron age finepottery from Chatillon-s-Glane and the Heuneburg.Archaeometry, 24, 21-36.
Maggetti M., Neururer Ch. and Ramseyer D. (2011) -Temperature evolution inside a pot duringexperimental surface (bonfire) firing. Applied ClayScience, 53, 500-508.
Malek-Abbasi A., (2004) - Chogha Zanbil survived,but why?, 32th International Geological Congress,Italy, Florence.
Maniatis Y., and Tite M.S. (1981) - Technologicalexamination of neolithic-bronze age pottery fromcenteral and southeast Europe and from the NearEast. Journal of Archaeological Research, 8, 59-76.
Martineau R., Walter-Simonnet A.V., Grobety B. andBautier M. (2007) - Clay resources and technicalchoices for Neolithic pottery (Chalian, Jura,France), chemical. mineralogical and grain-sizeanalysis. Archaeometry, 49, 23-52.
Matson F. (1971) - A study of temperatures using infiring ancient Mesopotamian pottery. In R.H. Brill,Science and Archaeology (pp. 65-79). M.I.T. Press,
Periodico di Mineralogia (2012), 81, 3, 359-377
Emami et Trettin_periodico 19/12/12 14:33 Pagina 376
Mineralogical- chemical investigations on the ... 377
Cambridge.Mofidi Nasrabadi B. (2003) - Untersuchungen zu
Siedlungsstrukturen an der Peripherie von TschoghaZanbil (Dur Untasch). Archäologischer mitteilungenaus Iran und Turan (AMIT), 35-36, 241-265.
Monnin Y., Degrugilliers P., Butleed D. and Garcia-Diaz E. (2006) - Petrography of two siliceouslimestone’s submitted to alkali-silica reaction.Cement and Concrete Research , 36, 1460-1466.
Negahban E.O. (1991) - Excavation at Haft Tape.Iran. University Monograph 70, Philadelphia.
Noll W. (1991) - Alte Keramiken und ihre Pigmente,Studien zu Material und Technologie. D-7000Stuttgart: E. Schweizerbart’sche Verlagsbuchhandlung.
Okrusch M. and Matthes S. (2006) - Mineralogie.Germany: 9. Auflage, Springer Verlag, Berlin-Heidelberg-New York.
Oudbashi O. and Emami M. (2010) - A note oncorrosion morphology on some midlle elamitecopper aloy artefacts from Haft-Tappeh, south-westIran. Studies in Conservation, 55, 20-25.
Potts D. (1999) - The Archaeology of Elam:Firmationand Transformation of an Ancient Iranian State.Cambridge: Cambridge University Press.
Pownceby M.I. and Clout M.F. (2000) - Phase relationin the Fe-rich part of the system Fe2O3-Fe3O4-CaO-SiO2. Mineral Process and Extractive Metallurgy,109, 36-48.
Rathossi C., Pontikes Y. and Tsolis-Katagas P. (2010)- Mineralogical differences between ancient sherdsand experimental ceramics: Indices for firingconditions and post- burial alteration. Bulletin of theGeological Society of Greece, 2010, Proceedings ofthe 12th International Congress, Greece, Patras,May, 2010.
Salmang H. and Scholze H. (1983) - Keramik, Teil 2.Keramische Werkstoffe. 6. Auflage, Springer Verlag,Berlin, Heidelber, New York.
Szilágyi V., Gyarmati J., Tóth M., Taubald H., BallaM., Kasztovszky Zs. and Szakmány Gy. (2012) -Petro-mineralogy and geochemistry as tools ofprovenance analysis on archaeological pottery:Study of Inka Period ceramics from Paria, Bolivia.Journal of South American Earth Sciences, 36, 1-17.
Stoeklin J. (1968) - Salt deposits of the middle east.In R. B. Edited Mattox. International Conferenceon Saline Deposits (88, 158-181). Houston, Texas:Geological Society of America.
Sumner W. (1972) - Cultural Development in the KurRiver Basin, Iran; An archaeological Analysis ofSettlement Patterns. Philadelphia: Ph.D. Thesis,Departement of Anthropology, University ofPennsylvania .
Tehrani K. (1989) - Stratigraphy of Iran and TypeSections of Formations. Tehran: Tehran UniversityPublication.
Traore K., Kabre T.S., and Blanchart P. (2000) - Lowtemperature sintering of a pottery clay from BurkinaFaso. Applied Clay Science 17, 279-292.
Van der Voo R. (1993) - Paleomagnetism of theAtlantic, Tethys and Lapetus ocean, CambridgeUniversity Press.
Wong H.S. and Buenfeld N.R. (2006) - Euclideandistance mapping for computing microstructuralgradients at interfaces in composite materials.Cement and Concrete Research, 36, 1091-1097.
Submitted, July 2012 - Accepted, September 2012
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