Raman spectroscopic analysis of selected astronomical and ... spectroscopic analysis of the Book of... · Islamic ‘Book of Curiosities of the Sciences and Marvels ... The Engineering

JOURNAL OF RAMAN SPECTROSCOPYJ. Raman Spectrosc. 2006; 37: 865–877Published online 20 April 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jrs.1536

Raman spectroscopic analysis of selected astronomicaland cartographic folios from the early 13th centuryIslamic ‘Book of Curiosities of the Sciences and Marvelsfor the Eyes’

Tracey D. Chaplin,1 Robin J. H. Clark,1∗ Alison McKay2 and Sabina Pugh2

1 Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ, UK2 The Bodleian Library, Broad Street, Oxford OX1 3BG, UK

Received 17 October 2005; Accepted 20 January 2006

The Arabic treatise ‘Kitab Ghara’ib al-funun wa-mulah. al-‘uyun’ (‘The Book of Curiosities. . .’), whichcontains a series of important early maps and celestial diagrams has recently been acquired by TheBodleian Library. Previous examination of the text and paper has led to the suggestion that the manuscriptis an early thirteenth-century copy of a treatise compiled in the late eleventh century in Egypt.

The pigments and inks used for the illustrations on 11 folios selected from the treatise have beenanalysed using Raman spectroscopy in order to determine their compositions; SEM-EDX analysis hasbeen used to help identify one of the green pigments as a copper-based pigment. The combined analysisshows that the palette is relatively small in comparison with the wide range of colours observable, andconsists almost exclusively of cinnabar (or its synthetic equivalent, vermilion), orpiment, lazurite, indigo,a carbon-based black, basic lead carbonate (‘lead white’) and a copper-based green pigment, possibly aform of verdigris (found in only one of the maps).

The only comparable study (but by diffuse reflectance spectroscopy) of Arabic material was that of 17Arabic manuscripts from the eighth to the fifteenth century at the Bibliotheque nationale de France; thatstudy revealed a rather different range palette, which commonly included minium (red lead), copper greenand azurite, and mostly excluded indigo. However, 14 of the French manuscripts in the study were Qurans,and therefore not strictly comparable with the Bodleian manuscript, which is from a secular tradition.One of the three secular manuscripts in the French study, a thirteenth-century north African treatise(manuscript BN Arabe 2221), did have a remarkably similar palette to that of the Bodleian manuscript.This is a very small sample base from which to draw substantial conclusions, but the analysis of ‘The Bookof Curiosities’ forms a valuable starting point on which to build our knowledge of the production of Arabmanuscripts from this location and date. Copyright 2006 John Wiley & Sons, Ltd.

KEYWORDS: pigment analysis; Bodleian Library; Arabic manuscripts

INTRODUCTION

The Arabic treatise ‘KitNab GharNa’ib al-fun Nun wa-mulah. al-‘uy Nun’(The Book of Curiosities of the Sciences and Marvels for theEyes), recently acquired by The Bodleian Library, containsa series of early maps and celestial diagrams which are ofsignificant importance to the history of medieval cartogra-phy. The treatise consists of two books, the first pertainingto celestial (astrological and divinatory) matters and thesecond to terrestrial (descriptive and historical) matters. The

ŁCorrespondence to: Robin J. H. Clark, Christopher IngoldLaboratories, University College London, 20 Gordon Street,London WC1H 0AJ, UK. E-mail: [email protected]/grant sponsor: The Engineering and Physical SciencesResearch Council (EPSRC); Contract/grant number: GR/M82592.Contract/grant sponsor: Renishaw plc.

work, executed on paper, comprises 48 folios (96 pages) intotal, each measuring 324 mm ð 245 mm. These have beentrimmed previously from their original size with an associ-ated loss of some text and marginalia; many repairs have alsobeen made to the pages. The manuscript has been disboundfrom its recent Ottoman binding and is currently presentedas loose folios pending further exhibition requests. Previousexamination of the information supplied in the text and theconstruction of the paper has led to the suggestion that themanuscript is a copy made in c. 1200 of a treatise compiledin the late eleventh century in Egypt.1,2 The work includes:two world maps, one circular, one rectangular; maps of theIndian Ocean, Mediterranean and Caspian seas; maps of theMediterranean islands Sicily and Cyprus and of the cities ofal-Mahdıya (now Mahdia in Tunisia), and Tinnıs in the Nile

Copyright 2006 John Wiley & Sons, Ltd.

866 T. D. Chaplin et al.

delta; and unique maps of the Nile, Euphrates, Tigris, Oxusand Indus rivers.

Visual analysis of the illustrations in the treatise showsthat pigments of many colours can be observed includingred, yellow, orange, bright blue, dark blue, dark-, light- andmid-purple shades, dark green, olive green, brown-red andgold, with black (used for text and definition) and white (usedfor highlights) pigments also being used; in some cases, theorange pigment is associated with a purple-grey pigmen-tation. Eleven folios selected from the treatise have beenexamined using Raman spectroscopy in order to determinethe compositions of the pigments and inks used therein,and to distinguish between the original paint and over-paint. Possible areas of pigment decomposition have alsobeen examined with regard to establishing any degradationpathways. The folios examined are: 14a and 14b (illustra-tions of comets and stars) from the first book; and fromthe second book, 23b–24a (‘Rectangular World Map’), 26b(‘Inhabited Tree’), 27a (‘Wak-wak Tree’), 27b–28a (‘CircularWorld Map’), 32b–33a (‘Island of Sicily’), 34a (‘Island of al-Mahdıya’), 34b (text only), 35b–36a (‘Island of Tinnıs’) and43a (‘Oxus River’). Only the two world maps are orientedin keeping with traditional Arabic mapping practices withsouth at the top; the other maps have north at the top.

EXPERIMENTAL

The Raman spectroscopic analysis was performed in situusing a Renishaw System 1000 Ramascope, equipped withargon ion (� D 514.5 nm) and helium-neon (� D 632.8 nm)excitation sources at powers <0.4 mW at the object surface.The laser light was focused through the objective (ð20or ð50) of a Leica microscope onto each folio supportedon an extended microscope stage. The Rayleigh- andRaman-scattered light were collected back through the samemicroscope lens (180° backscattering geometry) and directedonto a holographic notch filter to remove the Rayleigh-scattered light. The Raman light was then directed ontoa thermoelectrically cooled CCD detector, operating at atemperature of �70 °C. The information from the detectorwas converted into a Raman spectrum using GRAMS32software operating on a standard PC. The spectra werecalibrated using the emission lines of a neon lamp, and bandsare reported to within an uncertainty of š1 cm�1. The spectraobtained were compared with those reported in publishedlibraries of spectra obtained from reference materials.3,4

The scanning electron microscopy-energy-dispersiveX-ray (SEM-EDX) analysis was performed using a JEOLelectron microprobe. A small sample from the surface ofFolio 27b–28a (‘Circular World Map’) was taken by rollinga cotton bud over the selected area of pigment. The unpol-ished sample was coated with carbon to aid analysis, andthe resultant peaks in the spectra from the sample werecompared with those of reference standards using INCAsoftware (Oxford Instruments Ltd).

RESULTS

Folio 14aFolio 14a, which forms part of the first book of the treatise,contains black text interspersed with astronomical illus-trations (Fig. 1(a)). Several comets are depicted in variousshades of red, orange and brown, the largest of whichis decorated with reflective golden flakes; a single star,located towards the centre of the page, is illustrated inblue. Raman analysis of these flakes decorating the largered-brown comet at the base of the page yields a spectrumwith no bands attributable to the gold pigment itself; onlybands attributable to cinnabar or vermilion from the sur-rounding red-brown pigment could be discerned (at 343, 285and 253 cm�1; as shown in Fig. 2(a)). Cinnabar and vermilionare soft mercury(II) sulfide pigments with ideal compositionHgS. Cinnabar forms as a natural deposit in certain volcanicand hot spring environments and has been used as a pigmentsince antiquity; vermilion, the synthetic form of cinnabar, hasbeen manufactured in Europe for use as a pigment since atleast the Roman period, often with natural cinnabar used asthe starting material.5 Raman spectroscopy cannot be usedto distinguish between the natural and synthetic productsbecause they have the same bulk composition and structure.As the background to the Raman spectrum obtained fromthe golden flakes is comparatively low with little or no flu-orescence, it is probable that the golden flakes are metallicgold. However, as most metals do not give a first-orderRaman spectrum, the actual presence of metallic gold cannotbe detected by this technique. Gold substitute materials usedas pigments, such as mosaic gold (a synthetic tin(IV) sulfidepigment, SnS2, made in China since 3000 BC)5 or certainmicas (natural potassium-rich aluminosilicate minerals), dogive spectra with many Raman bands. No such bands weredetected in the observed spectra of the folio and so the usethereon of these materials for the golden pigment can beexcluded.

The smaller comet depicted in the lower half of Folio 14a(Fig. 1(a)) is illustrated with a grey-brown pigment whosesurface is covered with a series of widely dispersed red-orange dots. Raman analysis of the grey-brown pigmentdemonstrates that it is a mixture of materials, yielding aspectrum containing intense bands from both vermilion (at343 and 253 cm�1, cf Fig. 2(a)) and orpiment (at 382, 358, 353,311, 292 and 203 cm�1; Fig. 2(b)), a naturally occurring arsenicsulfide mineral (As2S3�. Orpiment forms in nature as granularcrusts in the oxidizing zones of arsenic deposits and involcanic sublimates, where it maybe found with cinnabar.6,7

It has been used as a pigment since ancient times with itsearliest known use being in the decoration of wooden coffinsand stelae of Middle and New Kingdom Egypt, dated to the16th to 11th centuries BC;6,8,9 the earliest recorded examplesof synthetic orpiment are from the 15th century AD.8

It has been suggested by the conservation team thatthe grey colouration of the comet is a degradation product,

Copyright 2006 John Wiley & Sons, Ltd. J. Raman Spectrosc. 2006; 37: 865–877

Raman spectroscopic study of c.1200 Arabic scientific treatise 867

a b

d

f

c

e

Figure 1. Folios examined from the treatise, (a) 14a – comets and stars (Book I), (b) 14b – comets and stars (Book I),(c) 23b–24a – ‘Rectangular World Map’ (Book II, with south at the top), (d) 26b – ‘Inhabited Tree’ (Book II), (e) 27a – ‘Wak-wak Tree’(Book II), and (f) 27b–28a - ‘Circular World Map’ (Book II, with south at the top). All images reproduced by permission of theBodleian Library, University of Oxford.



Figure 2. Raman spectrum of (a) cinnabar/vermilion, (b) orpiment, (c) lazurite, (d) lead(II) carbonate hydroxide, (e) carbon-basedblack, (f) indigo (each collected using 632.8 nm or 514.5 nm excitation, a 50ð objective and approximately 0.35 mW laser power atthe sample surface).

perhaps of red lead. However, the Raman analysis showsthat the pigment does not contain lead (II, IV) oxide,but only orpiment and vermilion. Although orpiment isknown to darken under certain conditions6,8,10 degrading

to a brown colour, the orpiment crystals observed hereappear fresh, suggesting that the pigment remains close toits originally intended colouration. The red-orange pigmentused to annotate the surface of the comet is present in a



layer sufficiently thick to exclude any contribution from thebackground material. Raman analysis of this pigment showsthat it also is a mixture of orpiment and vermilion, yieldinga combination of the spectra shown in Fig. 2(a) and (b).

Analysis of the blue pigment used to illustrate thesmall star close to the centre of the folio (Fig. 1(a))shows that this material is lazurite, which characteristicallyproduces strong bands in the Raman spectrum at 548and 1096 cm�1, and weaker bands at 1904, 1641, 1356,808, 583 and 259 cm�1 (Fig. 2(c)). Lazurite is a sodium-and calcium-rich aluminosilicate mineral with composition(Na,Ca)8[(Al,Si)12O24]Sn, in which the blue colour is causedby the presence of sulfur radical anions.11 – 14 It formsin metamorphosed limestones and marbles in which themetamorphism is associated with alkaline volcanic activity.Lazurite commonly occurs with calcite and pyrite to formthe rock type known as lapis lazuli and it is the lazuritecomponent that gives the rock its blue colour. Lapis lazuli(and lazurite) is best known from the Kokcha River valley(Afghanistan), mined for more than 6000 years and believedto be the source of most of the lazurite used for decorativepurposes.6,15

Folio 14bFolio 14b, also from the first book of the treatise, contains bothblack and red text, with three comets illustrated (Fig. 1(b)).The grey pigment used to illustrate the comets was examinedin order to determine whether it is original or a degradationproduct; the composition of the black ink used for thetext was also examined. Raman analysis of the head ofthe third comet indicates the presence of lead(II) carbonatehydroxide (the most common ‘lead white’ pigment), withcharacteristic intense bands observed in the spectrum at1049 and 1053 cm�1 (Fig. 2(d)). Lead(II) carbonate hydroxide(2PbCO3ÐPb(OH)2) is one of the earliest synthetic pigments,manufactured since antiquity through the action of anacidic organic substance (such as vinegar) on metallic lead.Although a natural analogue of this lead carbonate exists (themineral hydrocerussite), it is a rare mineral and is not thoughtto have been used as a pigment.6,16 Lead whites are alsodocumented as darkening under certain conditions owing tothe transformation of the basic lead carbonate to black leadsulfide (PbS) or brown lead dioxide (PbO2).16,17 Examinationof the black ink used for the medium-large Naskh scriptwas carried out at close to the centre of the ninth line fromthe top of the page. Analysis of the ink yielded a Ramanspectrum with two broad bands centred at approximately1590 and 1360 cm�1 (Fig. 2(e)). These bands are characteristicof a low-crystalline carbon-based black material.

Folio 23b–24a (‘Rectangular World Map’)The map depicted on Folio 23b–24a (Fig. 1(c), with southat the top) is considered to be the only rectangular worldmap preserved from antiquity or from the medieval world.1

The green, blue and purple pigments used on the map to

illustrate the oceans, seas, rivers and the ‘Mountain of theMoon’ were analysed at seven sites in order to determinetheir compositions. The dark green pigment used for the seasand oceans was examined at the western end of the illustratedMediterranean sea, south of the broad Iberian peninsula.Under the microscope the pigment is seen to be composedof a mixture of fine-grained blue-green particles and largereuhedral yellow grains bearing striated surfaces. The Ramananalysis shows that the yellow grains are orpiment, withcharacteristic bands observed in the spectrum as shown inFig. 2(b). By contrast, the spectra obtained for the green-blueparticles at this site are dominated by fluorescence, whichobscures any Raman bands related to the material itself.Thus, the composition of the green-blue component couldnot be determined. The dark green pigment appears to havebeen applied over a lighter green paint layer in some areas.This is particularly evident along the depicted coastlines ofthe Mediterranean sea where the underlying lighter greenlayer is exposed. This pigment is visually distinct from thedarker green overpaint, as no yellow orpiment crystals areobservable within it. Raman analysis of the lighter greenpigment was performed close to the illustrated north Africancoastline, south of Iberia. However, no Raman bands couldbe identified in the spectra obtained from this material either,because of the high fluorescent background.

Significant repair work has been undertaken across thecentral fold of the folio, particularly in the northern areaof the map, where the marine areas have been repaintedwith another green pigment. Under the microscope, it maybe seen that this pigment is a mixture of yellow and blue-green particles, similar to the mixture observed for the darkgreen pigment used to illustrate the Mediterranean sea.The two pigments are however visually distinct, with thepigment used for the repaired area having a much finergrain size, with no coarse-grained yellow crystals present.Raman analysis of the repair work shows that the yellowgrains in the pigment mixture also yield spectra as shownin Fig. 2(b). Once again, the composition of the blue-greencomponent of the pigment could not be determined owingto the significant amount of fluorescence afforded by it.

Under the microscope it may be seen that the dark blue-purple pigment used to illustrate the semicircular ‘Mountainof the Moon’ (positioned at central southern part of the map)is composed of a vitreous red pigment with a small numberof very fine-grained dark aggregates also present. Ramananalysis of the red material shows that it is cinnabar (or thesynthetic equivalent vermilion), with characteristic bandsobserved in the Raman spectrum at 343, 285, and 253 cm�1

(cf Fig. 2(a)). Similar analysis of the dark aggregates showsthat they are composed of a carbon-based black material,with two diagnostic broad bands present in the Ramanspectrum at ¾1590 and 1360 cm�1 (Fig. 2(e)). Through naturaldesiccation cracks in this blue-purple pigment an underlyingorange pigment layer composed of a mixture of orange-redand yellow crystals can be observed. Visual analysis suggests



that these crystals are vermilion and orpiment, respectively,although this identification was not confirmed by Ramananalysis.

The dark blue pigment used for the circular pools north ofthe ‘Mountain of the Moon’ is composed of a mixture of veryfine-grained dark blue particles and coarser-grained lightblue crystals. Analysis of this material close to the centre ofthe western-most drainage pool shows that the darker bluematerial is indigo, with characteristic strong bands observedin the Raman spectrum at 1584, 1575, 599 and 546 cm�1,and weaker bands at 1701, 1249, 277 and 252 cm�1 (Fig. 2(f)).Indigo (C16H10N2O2) is an organic blue pigment and a majordyestuff produced from the leaves of various indigofera plantspecies. It has been produced as a colourant since antiquity,commonly derived from steeping the plant leaves in analkaline solution (often water with slaked lime added) toinitiate the fermentation process. The pigment was widelytraded, with products from China and India coming toEurope via the Middle East.6,18 Similar analysis of the lighterblue crystals shows that they have a different composition,yielding bands in the Raman spectrum at 1904, 1641, 1356,1096, 808, 583, 548 and 259 cm�1 (cf Fig. 2(c)), indicative oflazurite. The Raman analysis therefore shows that this bluepigment is a mixture of indigo and lazurite.

The final blue pigment analysed on this folio is the paleblue material used for the Nile tributary depicted as drainingfrom the west of the map. Under the microscope this pigmentconsists of a finely crystalline dark blue material, with a fewcoarser-grained fragments also present. This material wasanalysed close to the depicted source of the river in fourclosely adjacent areas. The Raman analysis shows that thismaterial is indigo, with bands observed in the spectrumidentical to those shown in Fig. 2(f); no bands attributable tolazurite were detected, indicating that this blue material iscomposed only of indigo.

A further area of interest on the folio is the red and golddecoration surrounding the circular island (most likely SriLanka) depicted on the eastern side of the map in the IndianOcean. The red pigment in the decoration is shown by Ramananalysis to be cinnabar (or vermilion), yielding a Ramanspectrum identical to that shown in Fig. 2(a). Similar analysisof the adjacent gold decoration, however, is inconclusive asno bands are present in its Raman spectrum. As foundwith the analysis of the gold material present on Folio 14a(Fig. 1(a)), the spectra derived from this material were notdominated by fluorescence. Again this may indicate that thegold decoration is composed of metallic gold, which does nothave a first-order Raman spectrum. However, the presenceof gold metal cannot be proven here by this technique.

Folio 26b (‘Inhabited Tree’)Six sites on Folio 26b (Fig. 1(d)) were analysed in order todetermine the compositions of the five major pigments (darkblue, yellow, black, green and red) used to illustrate the‘Inhabited Tree’. Raman analysis of the dark blue pigment

used to depict the animals shows that this material is indigo,with the spectrum identical to that illustrated in Fig. 2(f).Selected areas of the animals are painted with a lighter bluepigment, which is at its palest close to the eyes of the animals.Analysis of this pale blue material, as used for the animalon the lower right-hand side of the tree, yields a spectrumcontaining characteristic bands of indigo as listed previously,and two further bands at 1053 and 1049 cm�1, indicative ofbasic lead carbonate (a ‘lead white’).

A yellow pigment has been used to depict the branches ofthe tree and the picture border on this folio. Raman analysisof this material, performed close to the end of the lowestbranch on the right-hand side of the tree, yields a spectrumwith bands at 382, 358, 353, 311, 292 and 203 cm�1 (Fig. 2(b)),indicative of orpiment.

Visual analysis of the black pigment used for theelongated leaves at the base of the tree shows that the pigmentis composed of anhedral black grains. Raman analysis ofthese particles, as observed in the largest of the black leaves,shows that they are a carbon-based black material with twobroad bands observed in the spectrum at approximately 1590and 1360 cm�1 (cf Fig. 2(e)).

The dark green pigment used for the pinnate leaves ontree branches appears under the microscope to consist of amixture of dark blue and yellow crystals; small areas of redpaint can also be observed within the leaves. Raman analysisof the green pigment mixture, as used for a leaf on the right-hand side of the tree, results in a complex spectrum in whichbands of both indigo (at 1701, 1584, 1575, 1249, 599, 546, 277and 252 cm�1� and orpiment (at 382, 358, 353, 311, 292 and203 cm�1� are present. Raman analysis of the red areas withinthe dark green leaves and of the red pigment used at the endsof the tree branches shows that this material is vermilion,with characteristic bands observed in the spectrum at 343,285 and 253 cm�1 (cf Fig. 2(a)).

Folio 27a (‘Wak-wak Tree’)The tree illustrated in Folio 27a shows human formsextending from its branches (Fig. 1(e)). Nine sites on thefolio were examined in order to determine the compositionsof the six major pigments (blue, yellow, red, brown-purpleand dark and pale green) observed in the illustration. Twoshades of dark blue have been used to decorate the base ofthe tree – the lighter blue has been used for the background,while a darker blue has been used to provide definition.Both pigments consist of small anhedral mid- to dark-blue particles and aggregates, the Raman analysis of whichshowing that they are both indigo, with bands observedin the spectra at 1701, 1584, 1575, 1249, 599, 546, 277 and252 cm�1 (Fig. 2(f)). No evidence was found for the presenceof any white pigment admixed with the indigo to make thelighter shade, which may therefore arise from a particle sizeeffect.

The illustrated tree is enclosed by a wide yellow border;a similar yellow pigment has also been used to depict the



ends of the tree branches from which the bodies extend.The material at the base of the border and at the top of theincomplete body on the left side of the tree is shown to beorpiment, which yields a Raman spectrum identical to thatshown in Fig. 2(b).

The bright red pigment used to illustrate the branches ofthe tree on this folio (Fig. 1(e)) is shown to be vermilion (cfFig. 2(a)). Visual analysis of the end of each branch allowsthe stratigraphy of the paint layers to be determined. It isclear from these areas that the red pigment was applied afterthe yellow layer (Fig. 1(e)).

Similar analysis of the brown-purple pigment used forthe bodies extending from the tree shows that it is a mixtureof red and blue components. The red component, as observedin the body depicted on the right side of the tree (Fig. 1(e)),is again shown to be vermilion yielding a spectrum identicalto that in Fig. 2(a). However, the Raman analysis of the bluecomponent is inconclusive, as no bands could be discernedin the spectra owing to the high degree of backgroundfluorescence.

The two green pigments used to illustrate the leaveson the folio each consist of a mixture of blue and yellowparticles in varying proportions. The darker green pigment,containing a larger blue component, has been used for themain bodies of the leaves, while the lighter green is presentas a highlight in some leaves and perhaps as an underpaintlayer in others. Raman analysis of the yellow particles, asobserved in the leaves at top of the tree (Fig. 1(e)), showsthat they are orpiment, with diagnostic bands observed in thespectrum at 353, 311 and 292 cm�1 (cf Fig. 2(b)). However, noRaman spectrum could be obtained from the blue componentowing to the significant amount of fluorescence imparted bythe material.

Folio 27b–28a (‘Circular World Map’)Folio 27b–28a (oriented with south at the top) shows theinhabited world surrounded by a dark blue ‘encompassingsea’. The map may be the earliest recorded copy of its typeand has greater detail with more extensive labelling thanany other known map of similar design.1 Sixteen sites onthe folio (Fig. 1(f)) were analysed in order to determinethe compositions of the four major colours (blue, purple,red-orange and green) used on the map.

The encompassing sea is illustrated with two differentblue pigments – a lighter blue which can be seen atseveral locations, exposed from beneath a darker blue-purple layer. The lighter blue pigment, thought to be theoriginal paint layer, consists of fine- to coarse-grained bluecrystals (<1–10 µm) with a broad grain-size distribution.The composition of these particles has been analysed at threelocations on the western side of the map, two of which(Fig. 1(f)) have the particles present at the map surface,while at the third, the crystals are observed through adesiccation crack in the overlying darker blue pigment. TheRaman analysis shows that these crystals are lazurite, with

characteristic bands observed in the spectrum at 1904, 1641,1336, 1096, 808, 583, 548 and 259 cm�1 (cf Fig. 2(c)).11 Thevariation in grain size may indicate that the pigment isderived from a natural source, as expected on a manuscriptfrom the thirteenth century. Lazurite was also identified asthe pigment used on the eastern side of the map to illustratethe small mountain range north of the large elongatedisland thought to be Java or the entire Malay archipelago1

(Fig. 1(f)). Here, the mountains are illustrated with a paleblue background of lazurite upon which dots of dark blueand red pigments have been applied.

Visual analysis of the darker blue pigment used for theencircling sea shows that it has an appearance different fromthat of the underlying lighter blue pigment. It is characterizedby a significantly smaller grain size, with individual crystalsdifficult to resolve at ð50 magnification. Raman analysisof this material at six sites on the western side of themap (Fig. 1(f)) demonstrates that the material is indigo,with diagnostic bands observed in the spectrum at 1701,1584, 1575, 1249, 599, 546, 277 and 252 cm�1 (Fig. 2(f)). Theseresults show that the encircling sea was originally paintedwith lazurite and has since been overpainted with indigo. Afew red particles at the surface of the indigo were determinedto be vermilion.

Pale purple pigments have been widely used on thefolio to illustrate various mountain ranges; these are oftenfurther decorated with evenly spaced dark blue and/or red-orange annotations. Visual analysis of the purple pigmentused for the semicircular ‘Mountain of the Moon’ and forthe small mountain range south of Java/Malaysia showsthat the pigment consists a mixture of fine-grained whiteparticles and larger (1–3 µm) red-orange crystals, with a fewwidely spaced blue crystals also present. Raman analysisof the white material (Fig. 1(f)) shows that it is basic leadcarbonate as determined from the two characteristic sharpbands present in the Raman spectrum at 1053 and 1049 cm�1

(Fig. 2(d)). Analysis of the admixed red-orange crystals attwo sites (Fig. 1(f)) indicates that they are vermilion, withcharacteristic bands observed in the Raman spectra at 343, 285and 253 cm�1 (Fig. 2(a)); no analysis was performed on theblue crystals comprising this pigment. The red material usedfor the red dots applied over the purple pigment (Fig. 1(f))was also determined to be vermilion.

Two green pigments used on the folio have beenanalysed. The first is dark green and used to depict theriver extending westwards to the circular sea. Ramananalysis of this pigment, considered to be overpaint appliedduring later restoration work, was performed close to thewestern extent of the river (Fig. 1(f)). This material yieldsa complex Raman spectrum that is clearly attributable toa mixture of indigo (bands at 1584, 1575, 599, 546, 277,and 252 cm�1� and orpiment (additional bands at 382, 358,353, 311, 292 and 203 cm�1�. The second green pigment,used for all of the river systems across the map, is palerand also considered to be part of the original decoration.



This material could not be identified by Raman microscopyowing to the significant amount of fluorescence affordedby it. The contrasting response to laser illumination ofthe indigo–orpiment pigment mixture and the paler greenmaterial suggests that the latter has a different composition.SEM-EDX analysis of a small sample of the pale greenmaterial shows that it contains a significant proportion ofcopper (Fig. 3). This result, together with the Raman resultson the samples, suggests that the pale green pigment is mostlikely a form of verdigris.19 Its identification solely on thismap may provide supporting evidence to the suggestion thatthis map was drawn by a different hand.1,2 The EDX dataalso show the presence of further elements such as arsenic,sulfur, lead, aluminium, calcium, potassium and chlorineand maybe attributed to the pigments surrounding the greenpaint (e.g. orpiment (As2S3�; lead white (2PbCO3ÐPb(OH)2);and lazurite (Na,Ca,K)8[(Al,Si)12O24](S,Cl)n�.

Finally, the black ink used for the fine script on theinterior of the map was analysed close to the circular poolnorth of the ‘Mountain of the Moon’ (Fig. 1(f)). This material,which has a glossy black appearance under a microscope,was determined to be a carbon-based black ink, as identifiedfrom the two broad bands in the resultant Raman spectrumat ¾1590 and 1360 cm�1 (Fig. 2(e)). This ink therefore has thesame bulk composition as that identified on Folio 14b.

Folios 32b–33a (‘Map of Sicily’)The map of Sicily is considered to be original to the treatiseand is unusual in that north is illustrated at the top of thepage, thus going against usual Arabic mapping practices.1

The orange, purple and yellow pigments used to depict thefeatures of Sicily were analysed at ten sites (Fig. 4(a)). MountEtna is depicted (incorrectly) at the western margins of themap of Sicily and is illustrated with a cusp-like annotationin two different shades of purple. The lower, interior partsof each cusp are decorated with a darker purple colour,while the outer areas are painted with a lighter purple.Under a microscope, the dark purple pigment is observed

as a mixture of small red, blue and black particles, witha few white particles also present. Raman analysis of thered grains shows that they are vermilion, yielding spectrawith characteristic bands at 343, 285 and 253 cm�1 (Fig. 2(a)).Similar analysis of the blue and black particles shows thatthey are indigo and carbon-based black, respectively, eachyielding spectra identical to those illustrated in Fig. 2(f) and(e). Raman analysis of the white particles is inconclusive,with no Raman bands discernible above the broad fluorescentbackground afforded by this white material.

The lighter purple pigment has a similar appearanceunder a microscope to the dark purple areas, consisting of amixture of red, blue and black particles. Raman analysis ofthe red and black grains shows that they are also vermilionand a carbon black, respectively, yielding spectra identicalto those shown in Fig. 2(a) and (e). However, analysis of theblue crystals observed in this pigment mixture shows thatthey are lazurite (yielding a spectrum cf Fig. 2(c)). Thus thelighter purple pigment used on this area of the folio has aslightly different composition (vermilion, carbon black andlazurite) from that of the darker purple pigment (vermilion,carbon black and indigo).

In one of the cusp-like areas (Fig. 4(a)) a solitary brightblue polycrystalline aggregate is observable, Raman analysisof which yields a complex spectrum containing many sharpbands at 2091, 2020, 1933, 1812, 1609, 1592, 1528, 1482,1450, 1408, 1341, 1322, 1306, 1214, 1143, 1127, 1107, 953,833, 775, 746, 699, 680, 610, 593, 482, 448, 259 and 233 cm�1

(Fig. 5). These bands are indicative of phthalocyanine blue,one of the modern blue pigments first produced in 1935.6

This pigment is therefore out of context on a thirteenth (oreleventh) century manuscript. This modern pigment grainmaybe present as contamination from an external source,such as a ballpoint pen or modern printed material, ratherthan as an integral part of the manuscript.

The black ink used to outline the design on the slopes ofMount Etna (Fig. 4(a)) was shown by Raman analysis to be acarbon-based black ink, with two characteristic broad bands

Figure 3. EDX spectrum obtained for one of the particles of green paint from the small river system at the western margin of Folio27b–28a (‘Circular World Map’ – Fig. 1(f)).



a b

c d

Figure 4. Folios examined from Book II of the treatise, (a) 32b–33a – ‘Map of Sicily’, (b) 34a – ‘The map of al-Mahdıya’, east at thetop, (c) 35b–36a - ‘The map of Tinnıs’, (d) 43a - ‘Oxus River’. All images reproduced by permission of the Bodleian Library,University of Oxford.

observed in the spectrum at ¾1590 and 1360 cm�1 (Fig. 2(e)).From the results, this ink is therefore shown to have thesame bulk composition as that identified on Folios 14b and27b–28a.

Several other mountain ranges illustrated at the marginsof the map of Sicily are depicted with a red-orange pigment

that is often associated with a purple-grey pigmentation(Fig. 4(a)). This darker pigment maybe an overpaint layeror a degradation product. Visual analysis of the red-orange material under the microscope shows that it iscomposed of a mixture dominated by fine-grained red-orange particles, with larger yellow and black particles



Figure 5. Raman spectrum of phthalocyanine blue with mainbands indicated (collected from Folio 32b–33a, site 1, using632.8 nm excitation, a 50ð objective and 0.04 mW laserpower).

present in smaller quantities. The grains comprising thismixture, as used for two of the mountain ranges on theeastern side of the island (Fig. 4(a)), was shown by Ramananalysis to comprise vermilion, orpiment and a carbon-basedblack, yielding bands in their individual spectra identicalto those shown in Fig. 2(a), (b) and (e), respectively. Thedarker purple pigment is visible under a microscope as amixture of red and black particles only; no additional yellowgrains (or obvious degradation products) are visible. Ramananalysis of this particulate mixture, performed at locationsin the north-eastern mountain range (Fig. 4(a)), shows thepresence of vermilion and a carbon-based black only, withno orpiment present. Although it has been documented thatorpiment may darken under certain conditions,6,8 degradedorpiment crystals when present retain many of their originalcharacteristic optical properties. No such crystals are visiblein this pigment mixture. The composition of the purple-greypigment (vermilion and carbon black) therefore suggeststhat it is present as an overpainted layer rather than as adegradation product of the underlying red-orange pigment.

A yellow pigment has been used to illustrate many fea-tures on Folio 32b–33a, including the dome of the ‘Ruler’sPalace’ east of the old city of Palermo, the gateways to theold city itself and to the pair of towers (‘Castle of the Chains’)on either side of the port of Palermo on the northern coast,and to delineate suburbs and quarters outside of the city. Theyellow pigment used for the domed roof of the Ruler’s Palaceis present as a very thin layer through which the underlyingpaper fibres are clearly visible. Raman analysis of this mate-rial is inconclusive as the spectra obtained are dominated bya highly fluorescent contribution from the paper fibres. Theyellow pigment used to illustrate the gateway of the tower

on the east side of the port has instead been applied in amuch thicker layer, resulting in a more crystalline appear-ance under the microscope. Raman analysis of this pigmentshows that it is orpiment (cf Fig. 2(b)).

A further red-brown pigment has been used to illus-trate the triangular-shaped mountain range located in thesouth-western corner of the island. Under the microscopethis pigment consists largely of red-orange grains, with afew dark blue crystals also present. The red-orange particlesin the central part of the mountain range (Fig. 4(a)) wereshown by Raman analysis to be vermilion (cf Fig. 2(a)). Sim-ilar analysis of the dark blue particles shows that they areindigo (cf Fig. 2(f)).

Folio 34a (‘The Map of al-Mahdıya’)The city referred to as al-Mahdıya in the Fatimid period(909–1171 AD), and now as Mahdia in Tunisia, is illustratedin Fig. 4(b). Raman analysis of certain pigments used toillustrate the map of this city was performed at nine sites onthe folio. The city walls are depicted with a purple pigment,which under a microscope is seen to be composed of purple-red grains set in a finer-grained white to pale purple matrix.Raman analysis of the purple-red grains resulted in spectrawith high fluorescent backgrounds being collected, with onlya single weak band discernable at approximately 225 cm�1.This band may indicate the presence of red ochre or haematite(iron(III) oxide, Fe2O3�, although this assignment is tentative.The use here of the purple minerals fluorite and amethyst canbe ruled out as these materials are strong Raman scatterersand yield spectra with bands at significantly higher wavenumbers.

The dark blue pigment used to illustrate the city buildingsconsists of large light blue to blue-purple crystals that havea broad grain-size distribution (<1–20 µm). Raman analysisof this material, performed on the pinnacle of a port buildingand on the dark cores of the building blocks of the westernpalace walls (Fig. 4(b)), shows that it is lazurite (cf Fig. 2(c)).The lighter blue pigment surrounding the dark cores ofthe building blocks was not fully characterized. The Ramanspectrum obtained for this material contains a single bandat 546 cm�1 (and no band of equal intensity at 599 cm�1�suggesting that this pigment also may be lazurite.

The palace and port buildings depicted on the folio havealso been decorated with a yellow pigment, Raman analysisof which, performed on the yellow gateway of the portbuilding (Fig. 4(b)), shows that it is orpiment (cf Fig. 2(b)).

Many of the red (and blue) building blocks of the palacewalls are decorated with a darker rectangular core that issurrounded by a pigment of a lighter shade. Raman analysisof the red ‘brickwork’ on the western side of the centralpalace building shows that the dark red centres (Fig. 4(b))are composed of vermilion (cf Fig. 2(a)). The surroundinglighter red-orange pigment was shown to be composed of amixture of vermilion and orpiment, yielding a more complexRaman spectrum with bands at 358, 353, 343, 311, 292, 253



and 203 cm�1 attributable to the two components. The samemixture was also identified as the red-orange pigment usedfor the building blocks on the eastern side of the building.

Folio 34b (Text)Folio 34b, containing text only, includes a catchword atthe base of the page. Raman analysis of the ink usedfor the catchword was performed in order to determinewhether this ink has a composition different from that usedelsewhere on the treatise. Examination of the catchword inkyields a Raman spectrum with two broad bands at ¾1590and 1360 cm�1 (Fig. 2(e)), indicative of a carbon-based blackmaterial. Identical spectra were obtained for the black textinks used on Folios 14b and 27b–28a, indicating that theinks have the same bulk composition (Table 1). However,this analytical technique is unable to detect possible tracedifferences between carbon blacks, which maybe indicativeof slight compositional variations.

Folios 35b–36a (‘The Map of Tinnıs’)The map of Tinnıs is considered to be one of the mapsoriginal to the treatise.1 Tinnıs was a commercial centre builton an island in the Nile delta and the map shows the islandwith the Mediterranean Sea depicted in green to the northand with the Nile deltaic lake (depicted in dark blue) on theremaining western, eastern and southern margins (Fig. 4(c)).Under a microscope it may be seen that the green pigmentused to depict most of the Mediterranean sea consists ofa mixture of green to dark green-black anhedral grainsand equant yellow crystals (up to 40 µm square) showingsurface striations. Raman analysis, performed close to theeastern end of the map (Fig. 4(c)) shows that the greenparticles are indigo (cf Fig. 2(f)), the green colouration beingmost likely caused by reflectance from adjacent or admixedyellow grains. Similar analysis shows that the yellow crystalsare orpiment (cf Fig. 2(b)). Selected areas of the sea havebeen in-filled with a darker green pigment. Visual analysisshows that this material is also composed of a mixtureof comparatively large yellow crystals and finer-grainedgreen to dark green particles, with anhedral black grainsalso present. Raman analysis of this composite material,performed on the rounded area of infill at the eastern end ofthe map, shows that the yellow grains are again orpiment (cfFig. 2(b)); in this case no Raman spectrum could be obtainedfrom the green particles. Raman analysis of the black grainsshows that they are composed of a carbon-based black (cfFig. 2(e)). The purple pigment used to illustrate the city wallsof Tinnıs consists of a fine-grained mixture of pale purpleand white materials, with a few larger red crystals also beingpresent (¾10 µm in size); it has an appearance similar to thepurple material used to depict the city walls of al-Mahdıya(Folio 34a; Fig. 4(b)). Raman analysis of the purple material atthe north-western corner of the walls (Fig. 4(c), site 3) yieldedspectra displaying high fluorescence over which only a veryweak Raman band at approximately 225 cm�1 is discernable.

Folio 43a (‘Oxus River’)The stylized map of the River Oxus (Amu Darya) (Fig. 4(d))shows the main body of the river depicted in a dark purple-blue pigment, with an additional dark blue line extendingalong the centre of the river; the outer margins of the riverare drawn with a black ink. Three sites on Folio 43a wereanalysed in order to determine the compositions of thematerials used to depict the river itself (Fig. 4(d)). Visualanalysis of the pigment used for the central blue line showsthat it is composed of light blue to dark purple-blue crystalsthat show a broad grain-size distribution (2–20 µm). Ramananalysis on the broad bend in the river (Fig. 4(d)) shows thatthese crystals are lazurite, (cf Fig. 2(c)). The dark purple-blue pigment used for the main body of the river was alsoanalysed along the bend in the river and shown to be indigo(Fig. 2(f)). The black pigment used to mark the edges ofthe river was examined at the western margin of the widebend in the river (Fig. 4(d)); it yields two broad bands in theRaman spectrum at ¾1590 and 1360 cm�1, indicating it to bea carbon-based black (Fig. 2(e)).

DISCUSSION

The Raman analysis of the pigments used for the illus-trations on selected pages of the treatise (Figs 1 and 4)demonstrates that the palette is relatively small by compari-son with the range of colours observable. Six pigments havebeen identified: cinnabar (or its synthetic equivalent ver-milion), orpiment, lazurite, indigo, carbon-based black andbasic lead carbonate (a ‘lead white’). These pigments havebeen used either individually or combined together as pig-ment mixtures to produce most of the colours present on thefolios (Table 1). Four further pigments used on several of thefolios could not be fully characterized: the golden material onFolios 14a and 23b–24a; a green pigment on Folios 23b–24aand 27b–28a; the purple pigment used to depict the citywalls on Folios 34a and 35b–36a; and the blue component ofthe dark green pigment mixture on Folio 23b–24a.

The concern over possible degradation of certain ofpigments on the folios examined here can now be addressed.Of particular interest is to establish the relationship betweenone of the orange pigments used on the map of Sicilyand its associated purple-grey surface layer (Folio 32b–33a,Fig. 4(a)). The orange material used on the eastern mountainranges has already been shown to be composed of vermilionand orpiment, mixed with a minor amount of a carbon-basedblack. No evidence to indicate the presence of lead (II, IV)oxide (Pb3O4 or ‘minium’), known to degrade and darkento lead sulfide (PbS) or lead oxides (PbO, PbO2� in certainmedia,6,20 was obtained. Examination of the purple-greypigment layer shows that it is composed of vermilion andcarbon-based black particles only, with no orpiment beingpresent. Although the darkening of orpiment under certainconditions has been documented,6,8 degraded orpimentcrystals where present often retain many of their original



Tab

le1.

Det

ails

ofth

ep

igm

ents

iden

tified

on11

folio

sfr

omTh

eB

ook

ofC

urio

sitie

s(U

ind

icat

esw

here

the

pig

men

tis

pre

sent

onits

own,

unm

ixed

;Min

dic

ates

whe

reth

ep

igm

ent

isp

rese

nton

lyas

par

tof

am

ixtu

re)

Folio

Des

crip

tion

Ver

mili

onO

rpim

ent

Ind

igo

Laz

urit

eC

arbo

n-ba

sed

blac

kB

asic

lead

carb

onat

e?H

aem

atit

eG

old

Phth

aloc

yani

nebl

ue

14a

Com

ets/

star

s(B

ook

I)U

CM

M–

U–

––

U–

14b

Com

ets/

star

s(B

ook

I)–

––

–U

M–

––

23b

–24a

‘Rec

tang

ular

Wor

ldM

ap’(

Boo

kII

)U

CM

MU

CM

MM

––

U–

26b

‘Inh

abit

edT

ree’

(Boo

kII

)U

UC

MU

CM

–U

M–

––

27a

‘Wak

-wak

Tre

e’(B

ook

II)

UC

MU

CM

U–

––

––

–27

b–2

8a‘C

ircu

lar

Wor

ldM

ap’(

Boo

kII

)U

CM

MU

CM

UU

M–

––

32b

–33a

‘Isl

and

ofSi

cily

’(B

ook

II)

MU

CM

MM

UC

M–

––

U34

a‘T

heM

apof

al-M

ahd

ıya’

(Boo

kII

)U

CM

UC

M–

––

–U

––

34b

Tex

tonl

y(B

ook

II)

––

––

U–

––

–35

b–3

6a‘I

slan

dof

Tin

nıs’

(Boo

kII

)–

MM

–M

–U

––

43a

‘Oxu

sR

iver

’(B

ook

II)

––

UU

U–

––

–



characteristic optical properties. No such crystals are visiblein this pigment mixture, suggesting that the composition ofthe purple-grey pigment (vermilion plus carbon black) isoriginal and that it is present as an overpaint layer, albeitincomplete, rather than as a degradation product of theunderlying red-orange pigment.

Degradation of one of the pigments used on the folioscannot be ruled out. Raman analysis of the grey pigmentused to illustrate the small comet on Folio 14b (Fig. 1(b))yielded the spectrum for lead(II) carbonate hydroxide only,a lead white pigment known to darken under certainconditions.16,17,20 Thus, the observed grey colouration of thispigment may be caused by possible darkening of the originallead white paint by way of a surface layer of black PbS.

CONCLUSIONS

Eleven folios from The Book of Curiosities have been analysedusing Raman spectroscopy with a view to determining thecompositions of the pigments used for the illustrations andtext, as well as understanding the relationships betweenoriginal and overpaint. The palette determined includescinnabar (or its synthetic equivalent vermilion), orpiment,lazurite, indigo, carbon-based black, basic lead carbonate(‘lead white’) and, in only one of the maps, a green copper-based pigment (possibly a form of verdigris); later overpaintapplied to the original copper-green pigment during morerecent restoration work has been established to be a mixtureof orpiment and indigo. Occasional use of red ochre and goldis indicated. The pigments identified have been used not onlyindividually but also in admixture in order to create a widerrange of colours. The conclusions that can be drawn from thecomparison ‘The Book of Curiosities’ and a thirteenth-centurynorth African manuscript analysed in a French study21 arelimited. However, the analysis is an extremely valuablestarting point for building up knowledge of the production ofsecular Arabic manuscripts from this time and location. Theidentification of certain pigments on ‘The Book of Curiosities’,particularly the light-sensitive orpiment and lead white,maybe important in the development of future conservationstrategies for this manuscript.

AcknowledgementsT. D. Chaplin acknowledges the support of the The Engineering andPhysical Sciences Research Council (EPSRC) (Grant GR/M82592)

and Renishaw plc. The authors also thank: the Bodleian Keeperof Oriental Books, Lesley Forbes; the research team of Drs EmilieSavage-Smith, Jeremy Johns and Yossef Rapoport; and Mark Barnardand David Jacobs from the British Library.

REFERENCES1. Johns J, Savage-Smith E. Imago Mundi 2003; 55: 7.2. Rapoport Y, Savage-Smith E. Cartograph. J. 2004; 41: 253.3. Bell IM, Clark RJH, Gibbs P. Spectrochim. Acta [A] 1997; 53: 2159.4. Burgio L, Clark RJH. Spectrochim. Acta [A] 2001; 57: 1491.5. Gettens RJ, Feller RL, Chase WT. Vermilion and Cinnabar; Artists’

Pigments, A Handbook of their History and Characteristics2. National Gallery of Art and Oxford University Press:Washington, DC, Oxford, 1993; 159.

6. Eastaugh N, Walsh V, Chaplin TD, Siddall R. The PigmentCompendium–A Dictionary of Historical Pigments. Elsevier Science:Oxford, UK, 2004.

7. Heinrich CA, Eadington PJ. Econ. Geol. 1986; 81: 511.8. FitzHugh EW. Orpiment and Realgar; Artists’ Pigments. A Hand-

book of their History and Characteristics 3. National Gallery of Artand Oxford University Press: Washington, DC, Oxford, 1997; 47.

9. Colinart S. Colour and Painting in Ancient Egypt. British MuseumPress: London, 2001; 1.

10. Cennini C. Il Libro del Arte. Dover: New York, 1960.11. Clark RJH, Franks ML. Chem. Phys. Lett. 1975; 34: 69.12. Clark RJH, Cobbold DG. Inorg. Chem. 1978; 17: 3169.13. Clark RJH, Dines TJ, Kurmoo M. Inorg. Chem. 1983; 22: 2766.14. Colomban P. J. Raman Spectrosc. 2003; 34: 420.15. Plesters J. Ultramarine Blue, Natural and Artificial; Artists’

Pigments. A Handbook of their History and Characteristics 2. NationalGallery of Art and Oxford University Press: Washington, DC,Oxford, 1993; 37.

16. Gettens RJ, Kuhn H, Chase WT. Lead White; Artists’ Pigments. AHandbook of their History and Characteristics 2. National Galleryof Art and Oxford University Press: Washington, DC, Oxford,1993; 67.

17. Smith GD, Derbyshire A, Clark RJH. Stud. Conserv. 2002; 47: 250.18. Schweppe H. Indigo and Woad; Artists’ Pigments. A Handbook of

their History and Characteristics 3. National Gallery of Art andOxford University Press: Washington, DC, Oxford, 1997; 80.

19. Chaplin TD, Clark RJH, Scott DA. J. Raman Spectrosc. 2006; 37:223.

20. FitzHugh EW. Red Lead and Minium; Artists’ Pigments. AHandbook of their History and Characteristics 1. National Galleryof Art and Cambridge University Press: Washington, DC,Cambridge, 1986; 109.

21. Deroche F, Berthier A, Guesdon M-G, Guineau B, Richard F,Vernay-Nouri A, Vezin J, Waley MI. Manuel de Codicologie desManuscrits en Ecriture Arabe. Bibliotheque nationale de France:France, 2002; 111.


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