Are carbon micro-clusters in the Khufu pyramid blocks of organic origin?
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VOL. 33 NO. 5 (2021)
ARTICLE
Are carbon micro-clusters in
the Khufu pyramid blocks of
organic origin?
PIXE and PIGE reveal the construction
of Giza’s pyramids
Guy Demortier
SPS and LARN, University of Namur and 61, rue de Bruxelles, B-5000 Namur, Belgium
The presence of carbon clusters of size ranging between 5 µm and 50 µm in samples of the Khufu pyramid identified with a
nuclear microprobe seems to indicate that they are of organic origin. Their location in the pyramid samples coincide with the
position of other clusters containing sodium. This situation is completely absent in limestone samples collected from Egyptian
quarries. The interpretation of the results could shed some light on the technique of construction of this huge monument.
Introduction Hawass, former minister of the Egyptian of mixed materials.9 In addition to the
The interdisciplinary approach of the Antiquities who was initially sceptical already reported elemental analysis of
technique of construction of the Big about the Morishima’s conclusions of Na, S and Cl associated with natural
Pyramids of Egypt is a subject of muon scans, is now ready to fully accept limestone we present here a possible
debate giving rise to passionate argu- them and suggest that this void could interpretation of abnormally incrusted
ments. Increasingly, scientific teams are be the location of the Khufu burial as 5–50 µm carbon clusters.
now being accepted on Egyptian sites reported in the Daily Express.3ruction
to perform non-destructive investiga- are to look at the structure of the monu- Experimental
tions of monuments. Recent discoveries ment as made by Bertho4 and by mate- arrangement
by Morishima and co-workers of large rials analysis as reported by Davidovits.5 Non-vacuum proton-induced X-ray emis-
cavities in the Khufu’s pyramid using These last two authors conclude that sion (PIXE) and proton-induced gamma-
cosmic-ray muons 1 have encouraged the monument was constructed with ray emission (PIGE) analyses of Egyptian
the Egyptian authorities to cooperate blocks moulded on site using local lime- pyramid blocks with low-energy protons
with Egyptologists around the World. The stone and binder (to produce a kind of produced by electrostatic accelerators
former reported length of the “big void” concrete) and not with hewn blocks. at the Universities of Namur and Lecce
(around 30 m long) is now believed to We have recently considered this point have shown abnormal concentrations of
be larger and continuous.2 The size of of view on the basis of the distribu- F, Na, S and Cl.10–12 More recently, micro-
this void is so large that it is clear that all tion maps of six major elements (C, O, PIXE and micro-PIGE investigations with
the surrounding structure must be highly Na, S, Cl and Ca) with a nuclear micro- a (in vacuum) scanning nuclear micro-
rigid: this rigidity can only be achieved probe. 6,7 This view is also supported probe at ATOMKI (Debrecen, Hungary)
with perfectly overlapping blocks. Zahi by Barsoum et al. who have used vari- (Figure 1) have been performed to
ous X-ray and electron microscopies to locally quantify the composition in lighter
demonstrate that pyramid blocks contain elements, down to carbon. The spatial
DOI: 10.1255/sew.2021.a21 calcium oxides and magnesium oxides resolution and uniformity of irradiation
© 2021 The Author with crystallographic structures which are were regularly checked on a copper grid
not found in natural materials.8 Recent deposited on a carbon substrate during
Published under a Creative Commons measurements of the orientation of the analysis (Figure 2).
BY-NC-ND licence iron compounds in pyramid samples Samples were taken from the inside
using paleo-magnetic methods support of chunks of Egyptian pyramid blocks
the hypothesis of a man-made tech- and from stone in the limestone quar-
nique giving rise to a rapid solidification ries of Tura and Maadi (north of Egypt).
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VOL. 33 NO. 5 (2021)
ARTICLE
They were crushed and pressed to
obtain flat circular pellets without
any additional binder (Figure 3). The
sampling process ensured that any
contamination with foreign material
was excluded. The flat surfaces were
irradiated with protons at normal inci-
dence with the following experimen-
tal conditions: 2.5 MeV proton beam
focussed to a spot size of ~3 µm,
beam current ~100–200 pA, size of
the scanned region 1 × 1 mm 2. The
measurement times were typically
~500–900 s corresponding to ~0.1–
0.2 µC accumulated charge.
Incident 2.5 MeV protons offer a maxi-
mum cross-section (100 %) for K-shell
ionisation of Al; 61 %, 84 %, 93 %,
Figure 1. The PIXE microprobe chamber at Atomki (Debrecen, Hungary). 98 %, 99.5 % for K-shell ionisation of C,
Figure 1 : The PIXE microprobe chamber of ATOMKI (Debrecen Hungary) O, F, Na, Mg and F, respectively (region
of decreasing slope of the K-shell ioni-
sation cross-section at Ep = 2.5 MeV);
and 87 %, 80 %, 73 %, 60 % and
53 %, respectively, for Si, P, Cl, K and Ca
(region of increasing slope of the K-shell
ionisation cross-section). This choice of
proton energy is optimum to partially
compensate for the unavoidable loss
of low-energy X-ray signals from light
elements (277 eV for CKa to 1.25 keV
for MgK a ) in the material, since the
K-shell ionisation cross-section increases
as protons enter deeper into matter. The
information depth for CKa , OK a and
Figure 2. Micro-PIXE maps of a copper grid on a carbon substrate. Left: copper; data collected CaKa X-ray lines in pure CaCO3 is given
Figure
with the Be 2 : Micro-PIXE
windowed maps
detector). Right: of a copper
carbon; grid onwith
data collected a carbon substrate
the SUTW detector.
in Figure 4.
( left copper : data collected with the Be windowed detector)
(rigth carbon :1cm
data collected with the super ultra thin window detector) The micro -PIXE detection setup
consisted of a super ultra-thin windowed
Outside block Khufu compressed pellet (SUTW) Si(Li) X-ray detector and a
Be-windowed detector which were oper-
ated simultaneously, allowing the effi-
Joining material Khufu as it is cient detection of light elements down
to carbon (in the 0.28–8 keV range) as
Joining material Khufu compressed pellet
well as heavier ones (from K upwards),
respectively. The SUTW detector was
Outside block Khufu as it is protected from backscattered particles
with a permanent magnetic unit. In
the case of the Be-windowed detec-
Outside block Khufu compressed pellet tor (solid angle ~100 msr) the intense
soft characteristic x-rays (
VOL. 33 NO. 5 (2021)
ARTICLE
C K-abs-edge Ca K-abs-edge
Micro-PIXE analysis of
Egyptian pyramid blocks
O K-abs-edge The choice of the positions of the SUTW
and Be-windowed detectors installed on
either side of the proton beam direction
(see Figure 1) was essential to check
the uniformity of the irradiated surface.
In order to avoid any misinterpretation of
the collected X-ray maps, it was neces-
pure CaCO3 matrix
sary to be sure that the structure of the
CaKa maps was the same in both detec-
tors. Shadowing effects due to poten-
tial irregularities along the pellet surface
would give rise to signal loss of X-rays
emitted by the lightest elements. It is
shown in Figure 8 that both CaKa maps
are similar for homogeneous (quarry)
and for non-homogeneous (pyramid)
Figure 4. Information depth for C, O and Ca in CaCO3. samples. The CaKa maps collected in
both detectors are similar but not iden-
Figure 4 : Information depth for C, O and Ca in CaCO3
tical in their intensity (counts are less
characteristic lines of elements from in the SUTW detector could indeed important in the Be-windowed detec-
CK a upwards as well as escape and suffer from partial interference with the tor than in the SUTW detector which
pile-up peaks present in the spectra are La line of Fe (705 eV): iron is indeed covers a higher solid angle). It can be
fitted. However, elemental concentra- present in all the analysed samples. seen that a Si cluster takes the place of
tions are calculated from the Ka or La The whole measurement procedure Ca in the top maps (Tura quarry). In the
X-ray intensities of elements, considering was calibrated and tested thoroughly middle maps (an outside block from the
the absorption-enhancement effects for with standard reference materials Khufu pyramid), clusters of Na and S are
characteristic X-rays within the samples (RMs), e.g. NIST 610, “Corning D” present in those regions missing Ca. For
as well as experimental parameters archaeological glass and some home- the bottom maps (an outside block from
(proton beam energy, detector solid made RMs, as well as pure chemi- the Khaphra pyramid), large Na clusters
angle, X-ray filters etc.) as described in cal compounds such as quartz, NaCl are present. These Na clusters have a
References 13 and 14. The micro-PIGE etc. On average, ~5–10 rel. % accu- very irregular shape that induces some
setup consisted of a NaI(Tl) detector racy can be achieved for the concen- apparent fuzziness which is certainly not
(diam. = 110 mm) placed outside the trations of major and minor elements due to the proton beam being out of
vacuum chamber at 90 ° relative to the and 10–20 rel. % for the trace element focus, but to large variations of thickness
direction of the beam. It was chosen for data. at their edges.
the detection of the 6–7.1 MeV g -ray Selected X-ray spectra of RMs, quarry The spatial distribution of all the
group of the 19F(p,ag)16O nuclear reac- and pyramid samples are given in elements is uniform in all quarry samples
tion, because FKa (677 eV) detection Figures 5–7. (Figures 9 and 10). Small inclusions
Figure 5. PIXE spectra collected by SUTW detector (left) and Be-windowed detector (right) on the homogeneous Corning reference material.
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VOL. 33 NO. 5 (2021)
ARTICLE
Figure 6. PIXE spectra collected by SUTW detector (left) and Be-windowed detector (right) on a limestone sample from Maadi quarry.
Figure 7. PIXE spectra collected by SUTW detector (left) and Be-windowed detector (right) on a sample of the external block of the Khufu pyramid.
Be windowed Si(Li) (SUTW) Si(Li) (around 15–30 µm in diameter) of Al, Si
and Fe can also be observed in addition
to nearly pure calcium carbonate (C, O
Tura
and Ca maps). Traces of Na, Mg, P, S, Cl
quarry and K show no specific spatial distribu-
tion. The elemental concentrations in Ca,
Ca Ca Si Mg, Al and Si were combined with the
appropriate O concentration to obtain
Ca the most probable chemical compounds:
Khufu CaCO3, MgO, Al2O3 and SiO2.
VT3
outside On the contrary, the distribution is
block very non-homogeneous in most of the
Ca Ca Na S pyramid samples, as shown in Figures
11–14. Beside abundant calcium
carbonate, there are inclusions (about
Kaphra
MYKF
20 µm wide or larger) of Na, Cl and/
outside or S which are correlated with a lack of
block
Ca and O. Sodium and chlorine (about
Ca Ca Na O 4–6 % and sometimes more) are
systematically correlated and could at
Figure 8.Figure 8 –Flatness check of pellet samples by comparison of CaKa maps in both detectors
Flatness check of pellet samples by comparison of CaKa maps in both detectors. first sight be interpreted as inclusions
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VOL. 33 NO. 5 (2021)
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Figure 9 – Distribution maps of 14 elements in Tura quarry sample (1mm x 1mm)
C O F Na Mg
Al Si P S Cl
CaCO3 96,8
MgO 1,21
Al2O3 0,26
SiO2 0,62
Na 0,15
Cl 0,06
Fe 0,1
K Ca Fe Sr
Figure 9. Distribution
Figure 10maps of 14 elements
– Distribution mapsin Tura
of 14quarry samplein(1Maadi
elements mm × 1quarry
mm). sample (1mm x 1mm)
C O F Na Mg
Al Si P S Cl
CaCO3 91,5
MgO 0,93
Al2O3 1,73
SiO2 4,41
Na 0,32
Cl 0,06
Fe 0,51
K Ca Fe Sr
Figure 10. Distribution maps of 14 elements in Maadi quarry sample (1 mm × 1 mm).
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VOL. 33 NO. 5 (2021)
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Figure 11 – Distribution maps of 14 elements in FH123 Khufu Great Gallery sample (1mm x 1mm)
C O F Na Mg
Al Si P S Cl
CaCO3 87,25
MgO 1,15
Al2O3 1,47
SiO2 4,90
Na2O 2,0
SO3 0,7
Cl 0,8
FeO 0,53
K Ca Fe Sr
Figure 11.Figure
Distribution
12 –maps of 14 elements
Distribution mapsinofFH123 Khufu Great
14 elements Gallery
in VT3 sample block
outside (1 mm of
× 1Khufu
mm). (1mm x 1mm)
C O F Na Mg
Al Si P S Cl
CaCO3 87,25
MgO 1,3
Al2O3 0,7
SiO2 5,24
Na2O 0,96
SO3 1,25
Cl 0,36
FeO 2,33
K Ca Fe Sr
Figure 12. Distribution maps of 14 elements in VT3 outside block of Khufu (1 mm × 1 mm).
26 SPECTROSCOPYEUROPE www.spectroscopyeurope.com
VOL. 33 NO. 5 (2021)
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Figure 13 – Distribution maps of 14 elements in 15a outside block of Khufu (1mm x 1mm)
C O F Na Mg
Al Si P S Cl
CaCO3 88,61
MgO 1,28
Al2O3 0,97
SiO2 5,18
Na2O 0,75
SO3 1,30
Cl 0,23
FeO 0,12
K Ca Fe Sr
Figure 13.Figure
Distribution
14 –maps of 14 elements
Distribution mapsinof15a
14outside blockinof15b
elements Khufu (1 mm ×
outside 1 mm).
block of Khufu (1mm x 1mm)
C O F Na Mg
Al Si P S Cl
CaCO3 88,61
MgO 1,28
Al2O3 0,97
SiO2 5,18
Na2O 0,75
SO3 1,30
Cl 0,23
FeO 0,12
K Ca Fe Sr
Figure 14. Distribution maps of 14 elements in 15b outside block of Khufu (1 mm × 1 mm).
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VOL. 33 NO. 5 (2021)
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of sodium chloride. Nevertheless, the in both Ca and O maps as shown in Conclusion
Na signal is always higher than what is the central upper part of maps, indi- Elemental distribution maps of C, O, Na,
needed to form NaCl (as confirmed by cates that the CK a line is produced S, Cl and Ca clearly indicate that the struc-
measurements on RMs). At the sites of deeper than 1 µm below the surface. ture of the samples of the Khufu pyramid
high concentrations of Na and Cl, the The volume of that C-rich region cover- is not homogeneous and is completely
Ca and O concentrations are less than ing a surface of 25 µm × 25 µm could different from samples from the Maadi
in the surrounding area. Considering extend down to 10–20 µm below the and Tura quarries. The amount of natural
that the oxygen content in Na 2O and surface. In addition, this region corre- limestone in pyramid samples is about
H2O is lower than in CaCO3, it may be sponds also to the region of both Na 5–10 % less than in samples from the
concluded that Na 2O (certainly with and Cl clusters: a probable signature of quarries. The other elements, like Na, S
some H 2 O) is mixed into the NaCl the use of natron (a naturally occurring and Cl, are mainly distributed in clusters.
clusters. Magnesium, phosphorus and mixture of hydrated sodium carbon- The mean concentration of Mg is higher
potassium are also more abundant in ate: Na2CO3 • 10H2O with some sodium in the pyramid samples, but this element
the pyramid samples than in the quarry chloride and sodium sulfate). All these is in general homogeneously distributed.
samples, but they are not distributed in observations fit with the model of Abnormal clusters of C with size varying
the clusters.6,7 Their presence may be construction created by Davidovits, from 5 µm to 30 µm are interpreted as
attributed to ashes used to create the who states that the blocks of Khufu from an organic origin. These structural
binder with a high chemical pH induced pyramid were cast in situ using granu- and compositional observations fit with
by Na2O and H2O.15 Reported concen- lar limestone aggregates, natron, lime the model of construction involving a
trations in Figures 10–14 have been (probably produced by the combustion moulding procedure.
computed with the data collected in of wood in domestic fires) and water It would be certainly important to
different regions of several irradiated to produce an alkali alumino–silicate understand why carbon is distributed
samples (6–10 different locations) and based binder.15 The black spot in the in clusters. 14 C dating would be the
do not only refer to the specific map. bottom-left part of the O map coincides best way to check this. If the C clus-
Beside calcium and magnesium oxides, with the bright spots in the Na and Cl ters observed by micro-PIXE originate
it is known that wood ash contains maps: the O content is indeed lower in from pollution, their 14C/12C ratio would
small quantities of oxides of phospho- Na2O than in CaCO3. The black spot in be the same as that for modern wood.
rus, potassium, manganese and iron.7 the bottom-right of the Ca map corre- If this ratio is lower by a factor of two
sponds to the bright spot in the Si map: (T ½ of C14 is indeed very close to the
Carbon clusters a small amount of SiO2 is common in reported age of the Giza pyramids!),
Carbon clusters have been observed on natural limestone as is also observed in the interpretation would suggest the
elemental maps collected on numer- the distribution maps of Figures 6 and 7. use of some organic material during
ous (but not all) pyramid samples, but A similar interpretation may be given the construction of the pyramid. A
14
never on maps from Maadi and Tura for sample VT3 (an outside block from C : 12C ratio close to zero would mean
quarry samples (see Figures 6 and 7) or Khufu) for C, O, Na, Cl and Ca maps that carbon is of geological age. As it
in other natural limestone samples from (Figure 13). Additional large clusters of is difficult to perform 14 C dating on
Belgium, Hungary and Saqqarah which Al, S and Fe justify the black spots in the very small samples like those used in
were analysed in the complete micro- Ca map. the present study, sampling with the
probe runs (more than 150 maps).6,7,16 Clusters of C in Figure 14 (sample 15B, agreement of the Egyptian authorities
The carbon maps refer to the detection an outside block from the Khufu pyra- could allow the appropriate quantity of
of the low-energy (277 eV) Ka line by mid) fully correlated with Na and Cl clus- material to be provided to experts in
the SUTW detector. This low-energy CK ters may be understood as discussed accelerator 14C dating. The conclusions
line, induced in pure CaCO3 by 2.5 MeV immediately above, but no clear of 14C dating would help lift the veil
protons, cannot reach the detector if its decrease is observed in the correspond- of mystery of the construction of the
production is deeper than 1 µm below ing Ca region. The C clusters are thinner Egyptian pyramids.
the surface (see Figure 4). However, than in Figure 12. C, Na and Cl clus-
if the carbon belongs to some organic ters are then concentrated closer to the Acknowledgements
compound, the information depth may surface allowing a better transmission of I am indebted to the scientific and techni-
be 5–10 times higher. Therefore, CK CaKa lines to explain the better uniform- cal staff of LARN (Namur, Belgium) and
could have been produced deeper which ity in the Ca map. The holes in the O ATOMKI (Debrecen, Hungary) for their
would explain the hole in the corre- map are in good correspondence with important support during the long runs
sponding Ca map. the clusters in the C, Na and Cl maps. of measurements. My special thanks to
The maps in Figure 12 refer to sample The C map of Figure 14 (same sample Prof. Á.Z. Kiss and Dr I. Uzonyi for fruit-
FH123 collected in the Great Gallery 15B but another fragment) shows a fila- ful advice and their valuable sugges-
of the Khufu Pyramid. A bright spot in ment-shaped distribution suggesting an tions concerning the nuclear microprobe
the C map, correlated to black spots organic origin. equipment.
28 SPECTROSCOPYEUROPE www.spectroscopyeurope.comVOL. 33 NO. 5 (2021)
ARTICLE
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Guy Demortier has a PhD in nuclear physics, is
Emeritus Professor of Physics at University of Namur,
Belgium, Co-founder and past director of LARN
(Laboratoire d’Analyses par Réactions Nucléaires),
Past-president of the Belgian Physical Society, Past-
president of COST Action G1 (Ion beam study of art
and archaeological objects) and First winner of the
EPS-IBA-Europhysics Prize for Applied Nuclear Science
and Nuclear Methods in Medicine. His research fields
include nuclear properties of light nuclei, neutron
physics, accelerator-based methods of elemental
analysis (PIXE, PIGE, RBS, RNA, XRF induced by PIXE,
nuclear microprobe), and applications in materials sci-
ence, archaeometry, ancient gold metallurgy, dentistry
and supraconductors.
https://orcid.org/0000-0001-6834-6866
guy.demortier@unamur.be
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