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Raman Spectroscopic Library

Raman Spectroscopic Library of Natural and Synthetic Pigments
Ian M. Bell, Robin J.H. Clark and Peter J. Gibbs Christopher Ingold Laboratories
University College London, 20 Gordon Street, London WC1H 0AJ, UK

The authors' research in this field was reported in the 21/2/98 edition of the New Scientist magazine, and one of their research papers has been selected as a 'Hot Article' for February 1998 by the American Chemical Society.

Click on the logo to access the relevant internet publications.

External link to "Hot Article"

Introduction to the site

Raman microscopy is now established as the technique that is most specific, sensitive, spatially refined and immune to interference for the non-destructive, in situ analysis of historical artefacts. To complement the increasing use of the technique in this field, the Raman spectra of sixty-four common pigments, both natural and synthetic, known to have been in use before ~1850 AD, have been studied by Raman microscopy.
Fifty-six pigments have yielded high quality spectra and these have been arranged here, by colour, into a spectroscopic library for reference purposes.

The pigment data have been arranged by colour into seven tables which can be accessed by clicking on the relevant link: black, blue, green, orange, red, white and yellow. The eight pigments that failed to give adequate spectra at either of the excitation lines used are included in a separate table. The spectra may be viewed by activating the link on the name of the pigment.

Spectroscopic files in SPC format may be downloaded via the spectra pages. They may be viewed in many spectroscopic software packages including Omnic (Nicolet Instruments: http://www.nicolet.com) and GRAMS/32 (Galactic Industries). A free viewer for SPC files, SPCView, may be downloaded from the Galactic Industries web page at http://www.galactic.com.

Warning
Before you proceed, please note that the wavenumbers quoted in the tables were obtained from spectra calibrated with Neon lines. We anticipate that the wavenumbers are accurate to ± 1 cm-1, except for bands marked as broad (br) or shoulder (sh) in the table. However, the SPC files have not yet been corrected and the band positions in the downloadable spectra may differ from those in the table.

USERS NOTE
Some users have experienced difficulty with the downloadable SPC files. The downloaded spectra have a gross non-linear distortion of the x-axis, which is nothing to do with the uncorrected band positions (see above statement). The SPC files have now been reloaded and are downloading correctly at our end. If any user experiences further problems, please contact the Webmaster. Thank you.

29th May 1998

Some Raman literature references to the pigments have been provided and clicking the link on the numbers in the tables can access these. To reference the authors' publications in the field of archaeometric analysis click here


Table of Black Pigments 

Name

Composition

Band Wavenumbersa / cm-1 and Relative Intensitiesb

Excitation Wavelength & Power

Notes and Datec

ivory black

carbon

961m (=n1(a1) PO43-); ~ 1325vs(br); ~ 1580vs(br)

632.8 nm
6 mW

Antiquity. Also contains calcium phosphate

lamp black

carbon

~ 1325vs(br); ~ 1580vs(br)

 

632.8 nm
6 mW

Antiquity

a Approximate centres of broad bands in the laser fluorescence spectrum.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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Table of Blue Pigments 

Name

Composition

Band Wavenumbersa /cm- 1 and Relative Intensitiesb

Excitation Wavelength and Power

Notes, Raman Literature References and Datec

azurite

basic copper(II) carbonate 2CuCO3.Cu(OH)2

145w; 180w; 250m; 284w; 335w; 403vs; 545w; 746w(sh); 767m; 839m; 940w; 1098m; 1432m; 1459w; 1580m; 1623vw

514.5 nm
2 mW

Mineral

cerulean blue

cobalt(II) stannate CoO.nSnO2

495m(sh); 532s; 674vs

514.5 nm
4 mW

1821

 

cobalt blue

cobalt(II)-doped alumina glass, CoO.Al2O3

203vs; 512vs

514.5 nm
4 mW

1775

Egyptian blue

calcium copper(II) silicate, CaCuSi4O10

114m; 137m; 200w; 230w; 358m; 377m; 430vs; 475m(sh); 571w; 597vw; 762w; 789w; 992w; 1012w; 1040w; 1086s

514.5 nm
4 mW

3000 BC. Also known as Cuprorivaite

lazurite

S3- & S2- in a sodium alumino-silicate matrix Na8[Al6Si6O24]Sn

258w; 548vs; 822w; 1096m

514.5 nm
4 mW

Mineral (lapis lazuli). 1,2,3,4 Synthetic c.1828 = ultra-marine

posnjakite

basic copper(II) sulfate CuSO4.3Cu(OH)2.H2O

135vw; 208vw; 278vw; 327vw; 467w; 612w; 983vs; 1092vw; 1139vw

632.8 nm
3 mW

Mineral

 

Prussian blue

iron(III) hexa-cyanoferrate(II) Fe4[Fe(CN)6]3.14-16H2O

282vw; 538vw; 2102m; 2154vs

514.5 nm
2 mW

1704. Earliest synthetic modern

smalt

cobalt(II) silicate CoO.nSiO2

462vs; 917m

514.5 nm
2 mW

~1500

a 1 cm-1.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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Table of Green Pigments 

Name

Composition

Band Wavenumbers / cm-1 and Relative Intensitiesb

Excitation Wavelength and Power

Notes, Raman Literature References and Datec

atacamite

basic copper(II) chloride, CuCl2.3Cu(OH)2

122m; 149m; 360w; 513vs; 821m; 846s; 911s; 974s

514.5 nm
4 mW

Mineral

chromium oxide

chromium(III) oxide, Cr2O3

221vw; 308w; 349w; 552vs; 611w

514.5 nm
4 mW

Early 1800s 5

cobalt green

cobalt(II) zincate CoO.nZnO

328m(br); 434vs; 471m(sh); 555s(br)

514.5 nm
4 mW

1780

emerald green

copper(II) ethanoate tri-copper(II) arsenite Cu[C2H3O2]. 3Cu[AsO2]2

122w; 154vs;175vs; 217vs; 243vs; 242vs; 294m; 325m; 371m; 429m; 492m; 539m; 637vw; 685w; 760w; 835w; 951m; 1355vw; 1441m; 1558m; 2926s

514.5 nm
0.5 mW

1814

malachite

basic copper(II) carbonate CuCO3.Cu(OH)2

155s; 178s; 217m; 268m; 354m; 433vs; 509m; 553s; 558w; 757vw; 1051m; 1085m; 1492vs

514.5 nm
1 mW

Mineral 6

Scheele's green

copper(II) arsenite Cu(AsO2)2

136s; 201m(br); 236w; 275m; 370vs; 445w; 495m; 537vw; 657vw; 780s

514.5 nm
2 mW

1778

terre-verte

Variations on K[(AlIII,FeIII)(FeII,MgII)],(AlSi3,Si4) O10(OH)2

145vs; 399w; 510w; 636m; 685m; 820vw; 1007m; 1084m

514.5 nm
1 mW

Mineral. The Raman spectra of other green earths may differ from that illustrated here

verdigris ('raw')

  

copper(II) ethanoate Cu(CH3COO)2

126m; 180m; 233m; 322vs; 703m; 949s; 1360w; 1417w; 1441w; 2943m; 2990w; 3027w

514.5 nm
1 mW

Synthetic (BC)

verdigris (no. 1)

  

basic hydrated copper(II) ethanoate [Cu(CH3COO)2]2.Cu(OH)2. 5H2O

139vw; 181w; 231w; 328w; 392w; 512w; 618w; 680w; 939s; 1351w; 1417m; 1441m; 1552w(br); 2937vs; 2988m; 3026w

514.5 nm
1 mW

Synthetic (BC)

verdigris (no. 2)

basic copper(II) ethanoate Cu(CH3COO)2. Cu(OH)2

193s; 271vw; 321w; 371w; 526m; 619vw; 676w; 939s; 1351w; 1424m; 1524w; 2939vs;3192m; 3476s; 3573s

514.5 nm
1 mW

Synthetic (BC)

viridian

chromium(III) oxide Cr2O3.2H2O

266w; 487vs; 552m; 585vw

514.5 nm
4 mW

1838 (?1850)

a 1 cm-1.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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Table of Orange Pigments 

Name

Composition

Band Wavenumbersa / cm-1 and Relative Intensitiesb

Excitation Wavelength and Power

Notes and Datec

Mars orange

Synthetic iron(III) oxide, Fe2O3

224vs; 291vs; 407m; 494w; 608m

632.8 nm
3 mW

Middle 19th C

a 1 cm-1.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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 Table of Red Pigments 

Name

Composition

Band Wavenumbersa / cm-1 and Relative Intensitiesb

Excitation Wavelength and Power

Notes, Raman Literature References and Datec

litharge

tetragonal lead(II) oxide, PbO

145vs; 285vw; 336w

632.8 nm
6 mW

Antiquity, cf. the yellow pigment massicot 7

Mars red

synthetic iron(III) oxide, Fe2O3

224vs; 291vs; 407m; 494w; 610m; 660w(sh)

632.8 nm
3 mW

Middle 19th C

purpurin

1,2,4-trihydroxy-anthraquinone C14H18O5

953m; 1019w; 1049m; 1091w; 1138w; 1160vw; 1229vs; 1312s; 1334s(sh); 1394s; 1452vs

632.8 nm
1.5 mW

Chromophore, with alizarin, in madder (3000 BC)

realgar

arsenic(II) sulfide, As4S4

142w; 164w; 171w; 182vs; 192s; 220s; 233m; 327vw; 342m; 354s; 367w; 375w

632.8 nm
0.6 mW

Mineral. 8,9,10 Undergoes a light induced transformation to the yellow compound pararealgar

red earths / red ochre

iron(III) oxide chromophore (Fe2O3 + clay + silica)

220vs; 286vs; 402m; 491w; 601w

632.8 nm
3 mW

Mineral

red lead

dilead(II) lead(IV) oxide: Pb3O4

122vs; 149m; 223w; 313w; 340vw; 390w; 480vw; 548vs

632.8 nm
3 mW

Antiquity 7

vermilion

mercury(II) sulfide, HgS

252vs; 282w(sh); 343m

632.8 nm
6 mW

Mineral 11,12 (cinnabar) and synthetic (8th C). May undergo a light induced transformation to black HgS

a 1 cm-1.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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Table of White Pigments 

Name

Composition

Band Wavenumbersa / cm-1, and Relative Intensitiesb

Excitation Wavelength and Power

Notes, Raman Literature References and Datec

barium white

barium sulfate, BaSO4

453m; 461w(sh); 616w; 647w; 988vs

514.5 nm
4 mW

Mineral 13 (barytes)

bone white

calcium phosphate, Ca3(PO4)2

431w; 590w; 961vs; 1046w; 1071vw

514.5 nm
4 mW

Antiquity

chalk (calcite)

calcium carbonate, CaCO3

157vw; 282vw; 1088vs

514.5 nm
4 mW

Antiquity 14,15

gypsum

calcium sulfate dihydrate CaSO4.2H2O

181w; 414m; 493w; 619vw; 670vw; 1007vs; 1132m

514.5 nm
4 mW

Mineral 16

lithopone

zinc sulfide and barium sulfate, ZnS and BaSO4

216w; 276vw; 342m; 453m; 461w(sh); 616w; 647w; 988vs

514.5 nm
4 mW

1874

lead white

basic lead(II) carbonate 2PbCO3.Pb(OH)2

667vw; 665vw; 687vw; 829vw; 1050vs

514.5 nm
4 mW

Rare mineral (hydro-cerussite). Synthesized in antiquity (pre-500 BC) 7

zinc white

zinc oxide, ZnO

331w; 383w; 438vs

514.5 nm
4 mW

1834

a 1 cm-1.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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Table of Yellow Pigments 

Name

Composition

Band Wavenumbersa / cm-1, and Relative Intensitiesb

Excitation Wavelength and Power

Notes, Raman Literature References and Datec

barium yellow

barium chromate BaCrO4

352m; 355m(sh); 403w; 427vw; 863vs; 901m

514.5 nm
4 mW

Early 19th C

berberine

[C20H18N1O4]+ plus sulfate or chloride anion

1203m; 1235w; 1276m; 1342w; 1361w; 1397vs; 1424w; 1449m; 1501s; 1518vs; 1568w; 1626s

632.8 nm
3 mW

Antiquity. Principal chromophore of the huangbo and kihada dyes

cadmium yellow

cadmium sulfide, CdS

304vs; 609s

514.5 nm
4 mW

Mineral (greenockite) and synthetic c. 1845

chrome yellow

lead(II) chromate PbCrO4

338w; 360s; 372m; 403w; 841vs

632.8 nm
6 mW

Rare mineral crocoite. Synthetic, 1809

chrome yellow deep

lead(II) chromate PbCrO4.PbO

336w; 358s; 374m; 401w; 838vs

632.8 nm
6 mW

Synthetic, 1809

chrome yellow-orange

lead(II) chromate PbCrO4.PbO

149m; 346w(br);828vs

632.8 nm
6 mW

Synthetic, 1809

cobalt yellow

potassium cobalt nitrite K3[Co(NO2)6].xH2O

179m; 274s; 304vs; 821vs; 836m; 1257w; 1326vs; 1398w

632.8 nm
6 mW

1861. Also known as Aureolin

gamboge

gambogic acids, C38H44O8 and C29H36O6

1215w; 1246.0m; 1265w; 1330w; 1433m; 1592s; 1633m

632.8 nm
3 mW

Before 1640, gum-resin

Indian yellow

magnesium salt of euxanthic acid MgC19H16O11.5H2O

484w; 610w; 631w; 697w; 772vw; 811w; 877vw; 1009vw; 1047w; 1097w; 1127s; 1178m; 1218m; 1266vw; 1345s; 1414w; 1476s; 1503s; 1599vs

632.8 nm
1.5 mW

15th century. Extracted from the urine of cattle fed on mango leaves

lead tin yelllow type I

lead(II) stannate Pb2SnO4

129vs; 196s; 275w(br); 291w; 303w; 379w; 457m; 525w

514.5 nm
4 mW

Antiquity? 17

lead tin yellow type II

silicon substituted lead(II) stannate, PbSn1-xSixO3

138vs; 324m(br)

514.5 nm
4 mW

Antiquity? Spectrum shown is of PbSn0.76Si0.24O3 17

Mars yellow

synthetic iron(III) hydroxide, Fe(OH)3

245w; 299m; 387s; 480w; 549w;

632.8 nm
1.5 mW

Middle 19th C

massicot

orthorhrombic lead(II) oxide, PbO

143vs; 289s; 385w

632.8 nm
6 mW

Antiquity, cf. the red pigment litharge 7

Naples yellow

lead(II) antimonate Pb2Sb2O7

140vs; 329m(br); 448w(br)

632.8 nm
4 mW

Synthetic (Egypt, 1570-1293 BC)

orpiment

arsenic(III) sulfide, As2S3

136w; 154s; 181vw; 202w; 220vw; 230vw; 292m; 309s; 353vs; 381w

632.8 nm
6 mW

Mineral 9,10, 18

pararealgar

arsenic(II) sulfide, As4S4

141w; 152w; 157vw; 171w; 174w; 190w; 195w; 202w; 222vw; 229vs; 235s; 273w; 319w; 332m; 344m

632.8 nm
1.5 mW

Light induced transformation product of realgar 9,10

saffron

crocetin, carotenoid dicarboxylic acid,C20H24O4

1165m; 1210w; 1282vw; 1536vs

514.5 nm
1 mW

Antiquity. Crocus flower stigma

strontium yellow

strontium chromate SrCrO4

339w; 348w; 374w; 431vw; 865vs; 893vs; 916m; 930w

514.5 nm
4 mW

Early 1800s

yellow ochre

goethite (Fe2O3.H2O ) + clay + silica

240w(sh); 246w; 300m; 387s; 416m; 482w; 551w; 1008s

632.8 nm
1.5 mW

Mineral

zinc yellow

zinc chromate ZnCrO4

343m; 357w(sh); 370w(sh); 409w; 772w; 872vs; 892m; 941m

632.8 nm
6 mW

1809 (commercial production, 1850)

a 1 cm-1.
b s = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad.
c The pigment is either specified to be a mineral or the date of its first manufacture is listed.

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Pigments with no detectable Raman signal using either 514.5 or 632.8 nm excitation

Colour

Name

Composition

Notes and Datea

black

magnetite

iron(II) di-iron(III) oxide,Fe3O4

Mineral. Transforms rapidly to Fe2O3 in the laser beam

Mars black

synthetic iron(II) di-iron(III) oxide,Fe3O4

Middle 19th C. Transforms rapidly to Fe2O3 in the laser beam

blue

indigo

indigotin,
C16H10N2O2

Plant leaf (BC)

brown

van Dyck brown

humic acids, allomelanins

Lignite containing iron (16th C?)

purple

Tyrian purple

6,6'-dibromo-indigotin
C16H10Br2N2 O2

Marine mollusc (1400 BC)

red

carmine

carminic acid, C22H20O13,
kermesic acid, C16H10O8

Scale insect, cochineal (Aztec) Scale insect, kermes (antiquity)

alizarin

C14H8O4

Secondary component (after purpurin) of the madder root dye (3000 BC)

yellow

quercitron

Flavonoid dye from the Quercus oak bark

 a The pigment is either specified to be a mineral or the estimated date of its first use is listed. 

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This site was originally compiled by P.J. Gibbs.

This page last modified 9 August, 2010

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