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Nuclear Instruments and Methods in Physics Research B 150 (1999) 591±596
Characterization of pre-Hispanic pottery from Teotihuacan,
Mexico, by a combined PIXE±RBS and XRD analysis
J.L. Ruvalcaba-Sil a,*, M.A. Ontalba Salamanca a, L. Manzanilla b, J. Miranda a,
J. Ca~netas Ortega a, C. Lopez b
a Instituto de Fõsica, UNAM, Apdo. Postal 20-364, Mexico DF 01000, Mexico
b Instituto de Investigaciones Antropologicas, UNAM, Circuito de los Institutos s/n, Ciudad Universitaria, Mexico DF 04510, Mexico
Abstract
A combined analysis of IBA techniques (Proton Induced X-ray Emission (PIXE) and Rutherford Backscattering
Spectroscopy (RBS)) and a complementary study by X-ray Di€raction (XRD) were performed to characterize pottery
corresponding to the Epiclassic period (A.D. 700±900) from Teotihuacan, Mexico. Elemental compositions of pottery
samples were measured by simultaneous PIXE and RBS using 2.6 MeV protons. Red, white and brown pottery pig-ments
were studied by non-vacuum PIXE and a proton beam of 3 MeV. The various mineralogical phases of the
pottery were identi®ed by XRD. From pottery elemental compositions and its mineralogical phases, some di€erences
among the pottery samples and groups were established. Ó 1999 Elsevier Science B.V. All rights reserved.
PACS: 81.70.Jb; 82.80.-d; 82.80.Ej; 82.80.Yc; 89.90.th
Keywords: PIXE; RBS; XRD; Archaeology; Pottery; Teotihuacan; Epiclassic
1. Introduction
Combined Proton Induced X-ray Emission
(PIXE) and Rutherford Backscattering Spectros-copy
(RBS) analysis has been used to study
material composition, especially in the case of
non-homogeneous materials. In particular, in the
case of arts and archaeology, the combination of
these techniques is the most suitable non-destruc-tive
method to determine the elemental pro®le of
artifacts, paintings and manuscripts [1±4]. As
ceramics is a quite stable material, pottery is
abundant in the archaeological context. A non-destructive
analysis is not always required: powder
samples and pellets can be prepared from pottery
fragments, being quite homogeneous by compari-son
to the original fragment. For archaeological
purposes, major elements and traces contents are
good enough to characterize the pottery material
and to determine the clay and its sources. From
this knowledge, information about trade routes
and relationships between cultures, and social
changes in ancient societies can be established [5].
In general, when simultaneous PIXE and RBS
is carried out on light and medium matrices, the
* Corresponding author.
0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved.
PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 1 0 7 2 - 6

592 J.L. Ruvalcaba-Sil et al. / Nucl. Instr. and Meth. in Phys. Res. B 150 (1999) 591±596
medium and heavy elemental composition mea-sured
by PIXE can be corrected and completed
with light elemental composition from RBS spec-tra.
Oxygen, carbon and silicon can be measured
taking advantage of their non-Rutherford back-scattering
cross sections for protons with energies
above 2 MeV. In this way, practically all elements
which are present in the pottery can be measured.
For special cases, like Na and F, Nuclear Reaction
Analysis (NRA) by (p,c) reaction can be used.
Ion beam analysis can be completed using other
techniques, such as X-ray Di€raction (XRD),
Energy Dispersive X-rays (EDX) or Scanning
Electron Microscopy (SEM). XRD is particularly
useful in the case of pottery because the main
mineral crystalline phases may be determined and
the amount of amorphous material can be esti-mated.
SEM analysis is used to study the mor-phology
of the pottery section and to obtain some
information about the temperatures, cooking clay
process and pottery fabrication. XRD may also be
used for this purpose [6].
In this work, we present the results of the study
of pottery samples from archaeological excava-tions,
byManzanilla [7], in tunnels at Teotihuacan,
Mexico, by simultaneous PIXE±RBS, non-vacuum
PIXE and XRD. The pottery samples correspond
to Epiclassic period of Mesoamerica (A.D. 700±
900) when the Teotihuacan culture decline started.
2. Archaeological context
During the Classic horizon (A.D. 0±900), the
®rst urban centers arose in Mesoamerica, the cul-tural
area comprising the Panuco river to Guate-mala
and Honduras. The Teotihuacan civilization
developed in the central high plateau of Mexico
from the beginning of this period and was the axis
of Mesoamerican life during the ®rst seven centu-ries
[8]. Teotihuacan was the largest and most
important urbanized and planned city in the whole
region: a monumental ceremonial core with huge
pyramids and grid of oriented streets and passages,
multifamily residential compounds, drainage sys-tems,
20 km2 of surface and a population between
40 000 and 200 000 inhabitants in its splendor. The
ancient city was a religious place and peregrination
center of ®rst order, as well a political capital. Its
in¯uence lasted through the rest of the pre-His-panic
Era. The main activity was craft: Teotihua-can
kept the control of obsidian sources in central
Mexico and established a strong monopoly on
pottery production and its distribution.
Teotihuacan sphere reached the Maya regions of
Guatemala. There are a lot of questions about
Teotihuacan civilization still without answer: the
real name of the city (Teotihuacan was the name
given by the people who arrived to the central part
of Mexico after Teotihuacan was abandoned) or
its language, for instance. By A.D. 650 starts the
decline of Teotihuacan. The origins of the decline
during the Epiclassic period are not clear: ruptures
of trade routes, internal revolts or depletion of
natural resources may be some of the reasons.
Pottery studies may provide some information
about its production, resources and distribution
during its decline. During the Epiclassic period,
vast demographic rearrangements occurred while
new politic and economic centers were established
in all Mesoamerica.
The studied ceramic samples are particularly
important because they come from carefully ex-cavated
primary contexts (domestic, storage, ritual
and funerary) from the tunnels behind the Pyra-mid
of the Sun, at Teotihuacan.
3. Samples and experimental setup
A set of 19 ceramic samples of di€erent typical
Teotihuacan tablewares corresponding to the Ep-iclassic
period and two sediments from the
Teotihuacan region were provided for this study.
Samples were taken from the sherds, and then
powder and pellets were prepared, taking care not
to include fragments of the painted surfaces.
The 3 MV Pelletron accelerator at IFUNAM
was used for the ion beam analysis. Our irradia-tion
chamber, commonly used for RBS and
channeling studies, was modi®ed in order to carry
out simultaneous PIXE and RBS analysis. A Si(Li)
detector was placed at a chamber window 30°
from the ion beam incidence direction, a Kapton
foil (12 lm thick) allows the detection of the
characteristic X-rays. Foils of 38 lm Al and 130

J.L. Ruvalcaba-Sil et al. / Nucl. Instr. and Meth. in Phys. Res. B 150 (1999) 591±596 593
lm Mylar were used as non-selective absorbers.
RBS detector was set at 168° from the ion beam
incidence direction. The samples were irradiated
by a 2.6 MeV proton beam using a collimator of 1
mm diameter. To avoid sample charging, an elec-tron
gun produced an electron spray on the sample
surface.
Paintings and pigments of several pottery
samples were irradiated on air using a typical ex-ternal
beam setup. The 3 MeV proton beam
crossed an 8 lm Al (exit window) and 1.5 cm of air
before reaching the sample surface with an energy
of 2.63 MeV. An Al foil (38 lm thick) was set at
the Si(Li) detector window as a non-selective ab-sorber.
The beam spot area at the sample surface
was 1 mm2.
On the other hand, the powder samples were
used for XRD analysis. A Siemens D-5000 dif-fractometer
with a Cu X-rays tube was used to
perform this study. The di€raction angle (h) ranged
between 2° and 70° to obtain the di€ractogram.
4. Results and discussion
4.1. Ion beam analysis results
RBS spectra of pellets were simulated by the
RUMP code [9] considering non-Rutherford
backscattering proton cross section for C, O and
Si. The light elements concentrations were con-sidered
to complete and to correct the elemental
composition calculated by PIXE. AXIL code [10]
was used to obtain the peak areas of PIXE spectra.
From Ka and La peaks and using the PIXEINT
program [11,12] it was possible to determine the
elemental composition. Oxygen and carbon in the
matrix were taken in account for ®nal results.
Table 1 shows the compositions of the pottery
samples and sediments. Typical uncertainties are
6% of the calculated value. Relevant elements for
pottery characterization depend on the geograph-ical
region. In this case, higher variations in the
concentration values were found when plotting
Ca, Fe, Ti, Sr and Zr concentrations vs. sample
number. A cluster analysis of the samples, con-sidering
Euclidean distance and simple linkage,
indicates that practically all of the pottery samples
form only one group, except for samples 17, 21
and the sediments, corresponding to samples 18
and 19 (Fig. 1). This means that samples 17 and 21
have a di€erent origin from the rest of the samples
[13]. The mean major elemental concentrations for
the group of potteries are 1.22% C, 45.7% O,
43.9% Al +Si, 2.31% K, 2.15% Ca, 0.19% Ti and
4.54% Fe while the trace elemental concentrations
are (in lg/g): 136 V, 470 Cr, 717 Mn, 62 Ni, 44 Cu,
114 Zn, 38 Ga, 85 Rb, 630 Sr, 269 Zr, 147 Pb.
Pottery 17 composition is quite di€erent in Al, Ca
and Fe. Pottery 21 concentrations are lower for Ca
and C, but O concentration is the highest for all
the samples.
As the colored regions of the potteries are quite
inhomogeneous, non-vacuum PIXE study was
only semiquantitative. Three samples (10, 11 and
13) were chosen as the most representative of the
decoration styles and the best preserved. AXIL
code was used to obtain the peak areas from PIXE
spectra and then to normalize to total the Ka and
La peaks areas. Iron, titanium and strontium
normalized areas were used to characterize the
colored regions of the potteries. A ternary diagram
(Fig. 2) shows the normalized peak areas, pottery
material normalized peak areas are also included.
Colored regions are well-de®ned for the di€erent
colors. Red regions are very rich in iron (pottery
10) but not for pottery 13, which has an Fe peak
normalized area similar to the pottery. A careful
examination of the red colored region of this
sample showed a deteriorated and non-homoge-nous
spoiled surface; thus, the beam could have
also reached the substrate of the colored region.
The rich iron red color can be associated to hem-atite
(Fe2O3). On the other hand, the white region
of the sample 13 is richer in Ti but poorer in Fe
and Sr than the rest of the analysis points. White
color may be associated to Ti oxides [14]. Light
brown and brown colored regions of sample 11 are
observed in the external and internal surfaces of
the pottery fragment. When comparing the col-ored
areas and the pottery, light brown area is
richer in Ti than the pottery and the brown colored
area, but not so rich as sample 13. A RBS analysis
using 3.05 MeV 4He‡ indicates that there is no
di€erence in the oxygen concentration between the
light brown and brown colored regions. Results

Table 1
Elemental compositions of 21 Teotihuacan samples determined by simultaneous PIXE and RBS analysis in vacuum (C, O and Al+Si measurements were measured from
RBS spectra. Uncertainties for RBS are 10% while for PIXE calculations are 6%)
Sample Elemental concentrations
(%) (lg/g)
C Colour Particularity C O Al+
Si
Ca Ti Fe V Cr Mn Ni Cu Zn Ga Rb Sr Zr Pb
1 Brown 1.84 45 43 2.45 0.206 4.48 103 347 698 54 28 108 37 90 751 359 184
2 Brown 0.00 46 44 2.19 0.192 4.60 106 392 790 44 46 112 30 84 581 252 90
3 Light
brown
Red paint 1.83 46 43 2.04 0.217 4.51 416 2040 218 59 45 114 47 91 757 187 133
4 Light
brown
Red paint 0.97 45 45 2.37 0.189 4.53 105 369 612 55 31 100 32 83 761 331 178
5 Light
brown
Orange 1.61 45 45 1.64 0.137 4.58 332 150 864 61 39 106 17 80 413 251 179
6 Light
brown
Orange 1.06 45 45 2.16 0.209 4.55 105 370 743 53 56 100 55 69 497 332 178
7 Light
brown
0.00 46 43 2.00 0.202 4.62 107 376 721 30 46 123 33 107 505 279 27
8 Light
brown
1.13 45 44 2.16 0.199 4.55 105 306 858 73 41 115 23 111 546 103 147
9 Light
brown
Red pigment 1.73 43 46 1.79 0.157 4.56 105 337 819 49 55 116 84 92 602 332 178
10 Light
brown
Red pigment 1.47 47 43 2.25 0.180 4.52 104 368 738 31 54 109 37 115 723 143 177
11 Light
brown
Brown and
light brown
1.17 46 46 2.26 0.208 4.53 105 335 815 75 24 115 28 57 572 331 73
12 Light
brown
Brown and
light brown
1.73 46 43 1.87 0.190 4.54 105 370 675 67 37 150 45 105 660 316 178
13 Light
brown
Orange paint-
White pigment
1.00 45 44 1.97 0.200 4.57 106 409 821 81 68 137 26 101 576 334 227
14 Light
brown
Orange paint-
White pigment
1.04 47 41 2.37 0.198 4.53 105 513 642 107 41 124 47 100 724 330 177
15 Light
brown
Red pigment 1.08 45 43 2.47 0.198 4.52 104 367 775 73 56 115 35 100 656 157 177
16 Light
brown
Red pigment 0.78 48 44 2.59 0.189 4.52 104 367 705 45 49 120 52 79 795 215 115
17 Orange Thin ware 1.94 40 40 4.18 0.141 4.30 99 303 581 68 58 11 19 100 407 93 115
18* Brown 1.48 49 41 0.30 0.163 4.72 109 275 1079 239 113 187 17 153 516 112 185
19* Brown 1.05 48 42 1.50 0.222 4.62 107 310 913 51 34 111 33 84 379 279 53
20 Brown Ligh brown 2.24 45 43 1.94 0.197 4.51 104 275 703 92 29 70 22 75 596 329 73
21 Light
brown
Red pigment-
Striates
19.18 38 36 1.50 0.159 3.82 88 341 515 65 ± 92 46 18 610 265 149

J.L. Ruvalcaba-Sil et al. / Nucl. Instr. and Meth. in Phys. Res. B 150 (1999) 591±596 595
Fig. 1. Elemental composition dendogram for the pottery and
sediments samples (Euclidean distance and simple linkage).
Carbon, oxygen and silicon+aluminium contents were deter-mined
from RBS.
indicate that a positive±negative decoration tech-nique
was applied.
4.2. X-ray di€raction results
The XRD semi-quantitative analysis indicates
that the main mineralogical phase of the pottery
samples 1±16 and 20±21 is albite, NaAlSi3O8,
and secondary phases of hornblende, (Ca,Na)2:26
(Mg,Fe,Al)5:15(Si,Al)8O22(OH)2, and quartz, SiO2.
Other main phase is anorthite, CaAl2Si2O8,
(samples 15,16, 21) and minor phases are
anorthoclase, (Na,K)(Si3Al)O8, (samples 8±10,
14, 15) and anortite (samples 12 and 13). The
main sediment phases are albite and anortite for
sample 18 and albite and hornblende for sample
19. The secondary phases are quartz, hornblende
and hallosyte (Al2Si2O5(OH)4) for sample 18,
while for sample 19 the secondary phases are
anortite, quartz and hallosyte. Contrarily, sample
17 is very rich in quartz, and the secondary
phases are composed by albite and anortite and
a minor phase of hematite (Fe2O3). In all the
cases, the amorphous part of all the samples was
estimated to be about 5±10%. From these re-sults,
it is noted that the mineralogical compo-sition
of sample 17 is very di€erent from the
other pottery and sediment samples (Fig. 3).
This fact agrees with IBA results and indicates
that sample 17 may have a di€erent origin than
sediments and the remaining potteries.
5. Conclusions
Simultaneous PIXE±RBS analysis combined
with XRD is a suitable method to characterize
and discriminate potteries. Despite the high
Fig. 3. Comparison between the XRD spectra of sample 17 and
a typical pottery sample of the group in dendogram (Fig. 1).
Sample 17 is rich in quartz while the other pottery samples are
rich in albite.
Fig. 2. Comparison of colored pottery regions of samples 10,
11 and 13 using normalized peak areas. Red, brown and white
colors can be distinguished; pottery material is also included.

heterogeneity of colors and styles of the studied
potteries, results indicate that a group is formed
with most of the potteries, but sediments are not
included. Some potteries do not belong to this
group (samples 17 and 21). Sample 17 presents
the highest elemental and mineralogical compo-sition
di€erences. This means that pottery 17 or
the clay used to manufacture it may have come
from a foreign procedence. In fact, it is a pottery
that is suspected to come from the Gulf coast of
Mexico. A similar interpretation may be
concluded in the case of pottery 21 which has a
Huasteca type (North-East Mexico area).
Red color paintings of the pottery of
Epiclassic period are associated to hematite while
white color can be associated to Ti oxide.
Contrarily, Ca compounds were used as white
pigment in Teotihuacan area during Classic
horizon. Negative±positive technique was applied
to produce brown light and brown decorations.
Acknowledgements
Authors thank Mr. K. Lopez for accelerator
operation during IBA measurements and Dr. R.
Valenzuela and Mrs. L. Ba~nos for the XRD
analysis. IFUNAMPelletron accelerator operation
is supported by CONACYT projects FO36-9109,
G0010-E and 127262E. M.A.O.S. acknowledges
the support of S.R.E., Mexico, for a scholarship.
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