Nuclear Instruments and Methods in Physics Research B 273 (2012) 173–177
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Nuclear Instruments and Methods in Physics Research B
journal homepage: www.elsevier.com/locate/nimb
Non-destructive provenance differentiation of prehistoric pigments by external PIXE
L. Beck a,⇑, H. Salomon b, S. Lahlil a, M. Lebon a,c, G.P. Odin a, Y. Coquinot a, L. Pichon a
a
C2RMF-UMR171 Centre de Recherche et de Restauration des Musées de France, 14 quai François Mitterrand, Palais du Louvre Porte des Lions, 75001 Paris, France
Centre Européen d’Archéométrie, Université de Liège, Sart Tilman Bât B15, 4000 Liège, Belgium
c
Muséum National d’Histoire Naturelle, Département de Préhistoire, UMR 7194, 1 rue René Panhard, 75013 Paris, France
b
a r t i c l e
i n f o
Article history:
Available online 26 July 2011
Keywords:
PIXE
Prehistoric pigment
Ochre
Provenance
Petrography
Arcy-sur-Cure
a b s t r a c t
The elemental analysis of minerals/rocks has been often used for the determination of their geological
origin. When these natural rocks were exploited by prehistoric civilizations as objects, weapons, or pigments, the composition of the minerals can provide information on the mobility, the exchanges and the
interaction between groups of population. In this paper, we will present results obtained from archaeological samples of prehistoric pigments, mainly iron and manganese oxides. PIXE analysis has been
applied to samples of the prehistoric cave ‘‘La grotte du Renne’’ in Arcy-sur-Cure, France (Chatelperronian, 38,000–34,000 BP). Because most of the archaeological objects are decorated or display some use
marks, it is not possible to take samples. Consequently, we have used a non-destructive technique thanks
to the external beam of AGLAE (C2RMF, Paris). In order to improve the limits of detection (LOD less than
10 ppm from Cu to Sb), a metal absorber has been placed on the X-ray detector to preferentially filter the
Fe–K or Mn–K lines.
Based on the quantitative analysis of major and trace elements, we have obtained groups of compositions corresponding to different geological sources. We demonstrate in this study that it is possible to
extend PIXE analysis to the characterization of prehistoric pigments such as iron and manganese oxides
for differentiating potential sources of pigments in archaeological contexts.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
In the past years, Particle Induced X-ray Emission (PIXE) has largely demonstrated to be a powerful tool capable of analyze trace
elements for determining the provenance of archaeological materials. It has been mostly applied to geological based material such as
obsidian [1–3] and gems [4–6]. In these cases, raw materials have
been employed by ancient civilizations without (or with minor)
transformation and it is admitted that the initial chemical composition is not (or slightly) affected [7]. This is particularly recognized
for trace elements which can be used as fingerprint of geological
sources and thus contribute to provenance investigations. This
point is an important question for historical and prehistoric studies, as it allows tracing commercial routes and cultural exchanges
between ancient communities.
Recent papers have focused on the study of trace elements in
pigments or in raw materials from geological sources by LA-ICPMS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) [8–10], PIXE [11–15] and neutron activation analysis [16,17].
Except Refs. [13–15] all the mentioned studies have required sample preparation which is not always possible for archaeological
⇑ Corresponding author. Present address: CEA, DEN, Service de Recherches de
Métallurgie Physique, Laboratoire JANNUS, 91191 Gif-sur-Yvette, France.
E-mail address: lucile.beck@cea.fr (L. Beck).
0168-583X/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.nimb.2011.07.068
artefacts. In this paper, we present experimental PIXE configurations which allow investigating prehistoric pigments, mostly iron
and manganese oxides, at the ppm level without any preparation
or sampling. In order to assess the feasibility of this procedure to
the study of pigment procurement, we have applied it to the prehistoric site of Arcy-sur-Cure, France (38,000–34,000 BP) [18,19].
2. Experiment
2.1. Pigment samples
Samples are composed of blocks of pigments found in the chatelperronian layers (38,000–34,000 BP) of la Grotte du Renne in
Arcy-sur-Cure, France. This site represents the richest archaeological sequence evidencing the late Neanderthal activities before
their complete disappearance. The excavations, conducted by André Leroi-Gourhan in the 60s, revealed a large amount of colouring
materials, mainly red or black. More than 18 kg of colouring materials, i.e. about 2000 fragments and 300 worked objects were associated with fireplaces and remains of two huts, which were built
with calcareous stones and mammoth tusks. All these observations
indicate intense production of powder either by crushing and
grinding, or by scraping and abrading. This last category of artefacts reveals consequently polished or striated surfaces (Fig. 1).
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L. Beck et al. / Nuclear Instruments and Methods in Physics Research B 273 (2012) 173–177
Fig. 1. Some blocks of pigments and worked tools (mainly in iron oxide (red) or in manganese oxide (black)) found in the chatelperronian layers (38,000–34,000 BP) of La
Grotte du Renne in Arcy-sur Cure, France. (For interpretation of the references to colours in this figure legend, the reader is referred to the web version of this paper.)
Due to the presence of marks on these worked tools which testify
of their use, it is not allowed to take sample for analysis. Objects
are consequently directly analysed without any kind of preliminary treatment or preparation.
2.2. PIXE experimental setup: external beam and selective absorbers
PIXE experiments were conducted at the AGLAE (Accélérateur
Grand Louvre d’Analyse Elémentaire, Paris, France) facility using
a 3 MeV proton extracted beam. The beam size is about 50 lm
diameter. Because the samples are highly inhomogeneous, they
were scanned in order to average over a 1 mm2 area. Objects were
just set on the XYZ table in front of the extracted beam exit. Precise
positioning is achieved by using the luminescence induced by the
proton beam on the sample minerals. X-ray spectra are recorded
by two Si(Li) detectors oriented at 45° to the beam [20,21]. One
is devoted to low energy X-rays (0.1–15 keV) from major elements
of the matrix, mainly Fe or Mn, Al, Si and Ca. The other detector is
equipped with selective filters to reduce pileup by attenuating intense X-rays [22]. We have selected absorber according to the matrix major element. For iron based matrix, a 20 lm thick chromium
absorber was mounted on the detector whereas for manganese
based matrix, a vanadium absorber was used. An additional
50 lm thick aluminium filter was superimposed in order to reduce
Cr or V X-rays induced by the interaction of the primary X-rays
coming from the sample with the absorber.
PIXE spectra were collected between 10 and 15 min (Fig. 2). Elemental concentrations have been extracted by using GUPIX [23]
and TRAUPIXE [24]. Thanks to this experimental procedure, limits
of detection less than 10 ppm have been achieved for most of trace
elements (Table 1). These values are of the same of order of magnitude as in other studies by NAA or PIXE where samples were
powdered and prepared.
groups). These results were obtained after a first mineralogical
determination by X-ray diffraction on a sampling of 80 blocks.
Then, nine blocks without any past modification tracks were cut
in order to prepare 30 lm thin sections studied with a petrographic microscope. Four groups are described as follow:
Group Aa: ferrugineous hardground. This rock is characterized
by benthic organisms, mainly crinoid segments and urchin remains
cemented by haematite, goethite and calcite. Its formation is the
result of an abrupt interruption of sedimentation lasting many million years.
Group Ab: this group presents the same morphology as Group
Aa, with a slight difference due to the dissolution of the carbonate
phase. Small bone fragments were also identified. This pigment is
formed in the same geological layer with the ferrugineous hardground but this part of the formation was submitted to water
activity.
Group B: ferrugineous sandstone/siltstone. This rock is characterized by 40–90% rounded quartz grains cemented by haematite
or a mix of haematite and goethite.
Group C: blocks of almost pure haematite. The lack of internal
structure within the blocks did not allow the identification of the
geological formation from which they were extracted.
For black pigment materials, the results obtained by this first
approach tend to show that the oxides and hydroxides of manganese form a homogeneous corpus (Group D) of black pigments
along the whole archaeological assemblage.
The study of the geological map and the research in the mining
archives have documented the possible catchment area for these
four minerals. The groups Aa and Ab are located around 40 km east
to the site in the Hettangian formations (beginning to the Jurassic),
whereas the group B has been identified in the Mio-Pliocene formation covering the tablelands next to the cave, around 4–40 km
west. For the groups C and D, no geological layer in the area of
Arcy-sur-Cure is documented.
3. Results
3.2. PIXE for iron oxide pigments
3.1. Mineralogical and petrographical characterization of the pigments
Based on mineralogical studies, Salomon et al. [19] have demonstrated that the red pigment materials found in the cave of
Arcy-sur-Cure have three different geological provenances (A–C
Twenty-seven samples corresponding to13 worked tools and 14
blocks were analyzed by PIXE. Around 20 of these samples were already characterized by petrography and/or XRD (see Section 3.1) to
be used as group references. Concentrations have been obtained
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L. Beck et al. / Nuclear Instruments and Methods in Physics Research B 273 (2012) 173–177
Si
Ca
10000
1000
22
Tl L
pile up
Ce
100
77
Counts
1- Low X-ray energy detector
Fe
Pb L
(a)
100000
18–45
3–9
26–80
1000000
La
60
10
1
15
20
25
30
35
40
2- High X-ray energy detector
with 20 µm Cr and 50 µm Al
Sb
Zn Rb
10000
Zr
Mo
100
Sn
Sr
Sb
Ba
25
30
Mo
10
7
2–8
11
As
1000
3
1–2
3
Counts
Fe
Ba
Mn
100000
14
10
24
4–10
56
5
8
0
1000000
3
1–2
4
17
Zr
Y
Sr
2
1–2
2
2
1–3
3
Rb
As
Ga
Zn
Co
Ni
Cu
for major and trace elements. Due to the irregular distribution of
fossil remains, totally or partially preserved, Fe and Ca cannot be
used to characterise the pigments. However, the Si:Al ratio gives
information on the alumino-silicate phase (Fig. 3). The alumino-silicate phases for groups Aa and Ab are composed of the same clay
mineral. Group B shows a high Si content which is due to the large
amount of quartz. Group C is not well defined.
In order to establish geochemical groups relative to iron oxide,
bivariate plots of iron and trace elements have been performed.
Among the 15 detected trace elements, three of them (Mo, As
and Sb) are correlated to iron with different ratios according to
Table 1
PIXE limits of detection (LOD) for elements heavier than iron.
Fig. 2. Typical PIXE spectra for prehistoric pigments composed of (a) iron oxide or
(b) manganese oxide. 1—Low X-ray energy detector (in blue). 2—High X-ray energy
detector (in red) equipped with a 20 lm thick selective filter and 50 lm Al. The
selective filters are Cr for iron matrix and V for manganese matrix. [Spectra ref:
09jun016-R437 and 18oct015- R598]. (For interpretation of the references to
colours in this figure legend, the reader is referred to the web version of this paper.)
12
2–4
12
(b)
3
3–4
6
40
3
5–10
7
35
7
8–9
11
20
Energy (keV)
19
15
57–100
30–54
145
10
Iron oxide matrix (this study)
Iron oxide matrix [12]
Manganese oxide matrix (this study)
5
0
4
1–2
10
1
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L. Beck et al. / Nuclear Instruments and Methods in Physics Research B 273 (2012) 173–177
900000
800000
y = -2.2194x + 635203
2
R = 0.221
Aa
700000
SiO2
600000
Ab
500000
C
400000
B
300000
y = 2.65x
R² = 0.92
200000
100000
0
0
20000 40000 60000 80000 10000 120000 140000 160000
0
Al2O3
Fig. 5. SiO2 concentration as a function of Al2O3 concentration (in weight%) for
prehistoric pigments composed of manganese oxides-hydroxides (Arcy-sur Cure,
France).
Fig. 3. SiO2 concentration as a function of Al2O3 concentration (in weight%) for
prehistoric pigments composed of iron oxide (Arcy-sur Cure, France).
the geological group (Fig. 4). Group C is characterized by a high
contents of Mo, As and Sb. Groups Aa and Ac have the same contents of As, Sb and Mo with intermediate values, confirming the
same geological origin. Group B has very low content in trace elements. These bivariate plots corroborate the source distinction
based on petrographic analysis, only performed on non-worked
blocks. Thanks to the PIXE results, it has been possible to precise
doubtful attribution of several archaeological samples. In particular, some attributions previously obtained by optical observation
and XRD were changed and two unidentified worked tools were
attributed to group B and group C (Fig. 4).
These results provide strong evidence that iron oxide sources in
the Arcy-sur-Cure area can be discriminated using external PIXE.
present in amounts not exceeding 10 wt%. Fig. 5 shows these oxides are closely correlated showing the homogeneity of the corpus
of samples. The minor and trace elements (Ce, Co, La, Y, Sr, Ni, Zn,
Cu, As, Zn, Mo) confirm this result. Four of them are presented in
Fig. 6. These data further demonstrate the uniformity of the manganese oxide corpus and evidence a common origin for all the samples studied.
4. Conclusion
External PIXE has been applied to analyse prehistoric blocks of
red and black pigments. Due to the archaeological importance of
the artefacts (38,000–34,000 BP), the analysis was performed directly on the samples, without any kind of preparation. The use
of selective filters has given access to limits of detection less than
10 ppm for iron-based pigments as well for manganese-based pigments. The quantification of trace elements provides chemical
3.3. PIXE for manganese oxide pigments
All the black pigment samples contain more than 70 wt% of
manganese oxide. Other major elements such as Si or Al can be
900
Mo
800
Aa
700
600
Ab
500
C
400
300
B
200
100
0
0
200000
400000
600000
800000
1E+06
Fe2O3
800
10000
As
700
Sb
600
1000
500
400
100
300
200
10
100
0
0
200000
400000
600000
Fe2O3
800000
1E+06
1
0
200000
400000
600000
800000
1E+06
Fe2O3
Fig. 4. Concentration (in ppm) of Mo, As, Sb trace elements as a function of the concentration in Fe2O3 for the prehistoric red pigments of Arcy-sur Cure, France. Two
unidentified samples (photographies) have been attributed by PIXE to groups B and C.
L. Beck et al. / Nuclear Instruments and Methods in Physics Research B 273 (2012) 173–177
177
Fig. 6. As, Cu, Zn trace elements as a function of MnO2 for the prehistoric black pigments of Arcy-sur Cure, France.
markers which allow establishing distinctions between different
types of red pigments.
These results provide strong evidence that prehistoric pigment
sources can be discriminated using external PIXE. It is one of the
main archaeological issues, in particular in the field of the chronological attribution of rock art and in the determination of colouring
provenance.
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