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8/3/2019 Abbas, H. Deterioration Rock Inscriptions Egypt. 2011
1/15
e-conservationthe online magazine No. 21, September 2011
8/3/2019 Abbas, H. Deterioration Rock Inscriptions Egypt. 2011
2/15
DETERIORATION AND
RATES OFWEATHERING
OF THE MONUMENTAL
ROCK INSCRIPTIONS AT
WADI HAMMAMAT,
EGYPT
By Hesham Abbas Kmally
8/3/2019 Abbas, H. Deterioration Rock Inscriptions Egypt. 2011
3/15
Introduction
In Wadi Hammamat there are outcrops for about
two kilometers of the Bekhenstone (conglomer
ates, silt stone and greywackes) that were quar
ried by the ancient Egyptians from the Predynas
tic times until the Roman period. These rocks,called the Hammamat formation, are a thick se
quence of late Precambrian age distributed in the
Eastern Desert of Eygpt. The Wadi Hammamat
area can be found halfway of the road between
Qift and Qusier. This area contains hundreds of
hieroglyphic and hieratic rock inscriptions (Fig
ure 1), texts that represent royal and private
names varying in length from a single word to
several lines. Some inscriptions show a numberof cartouches of several kings of Egypt who sent
several military and quarrying expeditions to ex
tract greywacke rocks. These rocks were used to
make several statues, vessels, sarcophagi and
other ornamental structural elements from the
Predynastic time to the Roman period. Romans
built watchtowers on the tops of the mountains
to guard the road, wells and quarries (Figure 2).
The Hammamat quarry still contains remains of
ancient quarrymen's huts on the north side of
QiftQusier road, built with dark greywacke and
silt stone (Figure 3). The region also includes Bir
Hammamat, located in the Central Eastern Desert
of Egypt at Wadi Hammamat, which is a Roman
watering station serving traffic travelling along
the QiftQusier road (Figure 4).
The Hammamat Group includes a thick sequence
of unmetamorphosed, clastic, coarsemedium
and fine grained sediments of molasse facies
[1, 2].
The Hammamat sediments formed by alluvial fan
braided stream [3] and composed mainly of con
glomerate, greywacke, arkose, siltstone andlittle of mudstone [4], are affected by a very low
grade regional metamorphism, characterised by
the presence of muscovite, sericite and chlorite
[5]. In time, the rock inscriptions were affected
by several types of deterioration, namely exfoli
ation, flakes, pits, joints, fissures, overloading,
thermal expansion, dissolution and salt efflores
cence. The Hammamat quarries have influence
by natural hazards, including torrential rains and
flash floods, salt efflorescence, mechanical and
chemical weathering. In most cases these hazards
DETERIORATION OF ROCK INSCRIPTIONS IN EGYPT
econservation 67
The famous ornamental stone known in antiquity as ''Bekhenstone'' comes from the Wadi Hammamat
area and it has been used for ornamental purposes since the ancient Egyptian times. The Wadi
Hammamat is one of the most ancient archaeological sites in Egypt because of the important rock
inscriptions scattered in the area, dating from before the earliest Egyptian dynasties to the late period.
These rock inscriptions suffered from serious damage due to natural weathering, pollution, salt
efflorescence and other physicochemical weathering. Field observations referred that hard cement
mortars were used for repointing the greywacke rock inscriptions in Wadi Hammamat. The different rate
of expansion and contraction between the cement mortar and the greywacke rocks will eventually lead to
the separation of the two materials. This paper tries to clarify the main types of deterioration and
measure the chemical alteration and geological characteristics of the monumental greywacke rocks. In
order to achieve this, several studies were performed using a petrographic microscope, SEM micrographs,
Xray fluorescence and Xray diffraction analysis. The results have shown that the greywackes have a
moderate weathering and high content of ferromagnesian minerals.
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and weathering agents work together influencing
or strengthening each other. Moisture and rainsare considered the primary factors of deteriora
tion of the rock inscriptions in the studied area.
The interaction between the stone and moisture
or rain results in the appearance of destructive
subsurface patterns such as flaking, crumbling
and cracking of the stone surface.
Granular disintegration represents the most im
portant weathering process as result from thehydration and dehydration of salts and hydrolysis
processes. The intensive alteration of greywacke
rocks is very porous, individual mineral grains are
weakened and bonding between them is lostdu
ring wittingdrying cycles of moisture and salt
crystallisation, ultimately causing flakes and gra
nular disintegration of the inscriptions [6, 7].
In arid or semiarid regions insolation weather
ing, the alternating warming and cooling of rock
surfaces through solar heating, is capable of
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HESHAM ABBAS KMALLY
Figure 1. Example of rock inscriptions from Wadi Hammamat.
Figure 2. Roman stone watchtowers on the top of hills.
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econservation 69
breaking up rock inscriptions through thermal
action [8]. Insolation weathering causes fracture
of the minerals on the rock surface while the
great temperature difference between the rock
layers causes exfoliation [9], making the grey
wacke rock to become weaker and more deform
able. The majority of the rock fragments and
different grains in the Hammamat sediments are
composed of several elements with different
chemical weathering. Thus, the major element
contents (wt%) in the sedimentary rocks were
used for calculating the rate of chemical altera
tion and paleoweathering conditions [1014].
Materials and methods
Fresh and weathered samples were collected fromthe rock inscriptions at Wadi Hammamat. The
altered samples of siltstone and greywacke sur
faces were studied by polarizing microscopy (PL),
scanning electron microscopy (SEM), Xray fluo
rescence (XRF) and Xray diffraction (XRD) to
determine their mineral composition, alteration
products, morphological and the degree of chemi
cal weathering. The major elements of greywacke
rocks were determined by XRF at the central labo
ratories of Egyptian Geological Survey, Cairo. Grey
wacke samples were coated with gold and examined
by SEM in the laboratories of the Scientific Mobark
City in Alexandria.
The present study tries to define the deterioration
features and describe the conservation state of
the rock inscriptions in Wadi Hammamat. A de
tailed petrographic study covering about 20 thin
sections was also performed.
Results and discussion
Field observation
Through a complete survey carried out by visual
observation and digital photography at Wadi
Hammamat quarries, we realised that there are
different deterioration processes with varyingdegrees of weathering and decay features in the
studied area. According to Fassina, all sediment
ary, metamorphic and igneous rocks exposed to
a weathering agents deteriorate continually as a
result of physical and chemical processes [16].
Geologically, the Hammamat stone belong to the
sedimentary rocks and have several weakness
zones such as bedding, lamination, spherical and
oval nodules from soft material. These zones are
weaker than the rest of the rock, being more sus
Figure 3. Remains of workmen huts. Figure 4. Bir Hammamat, a Roman watering station for
travellers.
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ceptible to weathering and erosion. Mechanically
or structurally, the Hammamat stone inscriptions
are predominantly dissected by many joint setsof different attitudes and separated by weathering
processes as rectangular, angular and cuboidal
joint blocks (Figure 5A). The process of jointing
greatly increases the amount of surface space
exposed to weathering. These joints in the rock
allow the circulation of water and facilitate the
disintegration of minerals by hydrolysis processes,
leading to more mechanical and chemical weath
ering. Several small and large pieces of greywacke
are separated from the rock inscription walls due
to the combination of bedding planes and vertical
joints or inclined fractures (Figure 5B). It is also
worth mentioning that the fall down of greywacke
blocks lead to damage of many inscriptions.
Wadi Hammamat was subject to heavy rains in
1925, 1954, 1960, 1979, 1987, 1991 and 1996
with an average amount of rain fall of 40300x106
mm3 over the area [17]. Several flash floods werealso recorded in the Eastern Desert during the
last decades (1969, 1980, 1984, 1985 and 1994)
[18]. The rock slides in the area are attributed to
structural features and a period of very high rain
fall. The area has an arid desert climate, very high
moisture in the early morning, appearing as con
densation of water droplets on the surface of the
greywacke and siltstone. Rocks may deteriorated
and weaken by moisture and the action of watermay reduce the compressive strength of sandstone
up to 60% [19, 20]. The weathered rock inscrip
tion surfaces show a dark brown ferruginous layer
a few millimetres thick (Figure 5C) as a result of
chemical processes (water action) that change
ferrous iron to ferric iron in greywacke rocks.
Also, chemical weathering leads to dissolution of
calcite and clay nodules (Figure 5D) thatcreate
many fractures and extension fissures connected
with the empty nodules (Figure 5E). The relative
humidity (RH average) of the Eastern Desert
ranges between 43% in summer to 48% in winter,
while the temperature ranges between 21C and
41C and increase from north to south [18]. Thetemperature changes of the greywacke surface
are due to warming by the sun during the day
and cooling by night. The expansion and con
traction are important thermophysical factors
affecting their capacity to transform heat into
mechanical external energy (tensile and shear
ing stresses) leading to fractures and flakes in
greywacke rocks. Spalling and flaking were ob
served on the rock inscriptions as a result of the
thermophysical action (Figure 5F). Contour scal
ing phenomena was observed commonly in the
studied area as several lamellar parallel the grey
wacke surface as a result of thermophysical action
and salt crystallisation (Figure 5G).
Use of hard cement mortars for repointing
greywacke rocks
This is probably the most common form of humaninduced stone decay. Sedimentary rock walls need
to breathe through porous to allow water to
easily evaporate from them. Most cement mortars
are harder, massive and less porous materials, so
any evaporation is concentrated in the face of
the rock rather than in the mortars filling joints,
fractures and cleavages of greywacke rocks. This
result in soluble salts crystallising in the surface
layers of the greywackes and not in the adjoiningmortar leading finally to flakes and crumbles of
the rock rather than the pointing (Figure 5H).
Interactions between the atmosphere and grey
wackes or adjoining mortars lead to the formation
of altered surface layers and producing damage
in the original greywackes structure. The appear
ance of salt efflorescence deposits over the rock
inscriptions is common as a result of the reaction
of Portland cement with the rock and/or atmo
sphere pollution (Figure 5I). The main cause of
damage of the cement mortars and their adjoining
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Figure 5 (left to right, up tp down). Deterioration aspects of Hammamat quarry.(A) Several joint sets produced cuboidal jointing
blocks. (B) The vertical joints intersecting the bedding plane and inclined fractures lead to damage the rock inscriptions. (C) The
greywacke rock surfaces appear as a dark brown ferruginous layer. (D) Dissolution of calcite and clay nodules leads to serious
loss of rock inscriptions. (E) Extension fissures developing on the rock inscriptions. (F) The mechanical spalling in the rock in
scription. (G) Contour scaling on the greywacke surfaces as a result of high salt content near the surface. (H) Rock inscriptions flakesand crumbles as a result of repairs with Portland cement. (I) Whitish deposit over the surface due to the reaction of Portland ce
ment with greywacke rock inscriptions.
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rock inscriptions is probably sulphating formation,
in particular of gypsum and anhydrite. Sulphate
damage is closely related to the location of thecement repair, indicating that the sulphate source
is internal, obtained from a sulphurrich clinker
phase in the cement mortars. Sulphates are also
obtained from atmosphere pollution and soils.
The different rate of expansion and contraction
between the cement mortar and the greywackes
will eventually lead to the two materials separat
ing, a phenomenon referred to as bossing.
Petrography of the altered greywackes
(Polarizing Microscope)
A Greywackes
The examination of the greywacke samples thin
section under polarized light microscope showed
that the greywacke rock composed mainly of quartz,
plagioclase, epidote and lithic fragments of sand
size embedded in a finely crystalline pelitic groundmass (Figure 6A). The pelitic groundmass consists
of chlorite, calcite, quartz, muscovite, sericite,
epidote and iron oxides. Lithic fragments are
subangular to rounded, composed mainly of glassy
fragments and reworked siltstones. Quartz occurs
as subangular to subrounded grains and stained
by fine grained dust of ferric iron oxides as a
result of alteration. Some quartz crystals show
turbid colour, fractures and opening of microfractures as a result of mechanical external energy
(tensile and shearing stresses) (Figure 6B).
Plagioclase grains dissected by microfaults and
partially altered to epidote and sericite (hydro
mica) as a result of mechanical and chemical
weathering (Figure 6C). Also, some of the weath
ered plagioclase grain is completely kaolinitized
due to chemical weathering. In some slices, plagio
clase lamellae are bent as a result of deformation in
greywacke rock. Sericite occurs as randomly small
flakes and scaly aggregates that are frequently
interlacing the quartz and plagioclase grains. The
scaly aggregates of sericite f illing the fractures
in the quartz grains and replaced several plagioclase grains as a result of chemical activity of
water and mechanical stress action, ultimately
causes disintegration of the greywacke rocks.
Calcite occurs as original mineral either as alte
ration product of feldspar minerals or as a result
of the chemical alteration by water. It appears as
irregular patches scattered in the interspaces
between the other constituents as a cement joint
between grains and sometimes occurs as nodules
scattered through the greywacke rocks. Epidote
occurs as original mineral or as alteration products
of feldspar minerals. Chlorite occurs as original
mineral in the groundmass that cemented the
greywacke rocks. Chlorite coats the quartz and
plagioclase grains and gives the green pigmenta
tion of greywacke rocks. Iron oxides are repre
sented mainly by irregular granules, dust and
films of hematite covering the other mineralconstituents in the greywacke rocks. The grey
wacke appears stained with a dark brown colour,
indicating the presence of iron oxides suggesting
extensive invasion of water and exposure to
oxidizing conditions for a long period of time.
B Foliated greywackes
These rocks are fine grained, greenish grey incolour and foliated. They are composed mainly of
subangular to subrounded quartz, plagioclase,
clastic grains together with lithic fragments of
sand size set in fine grained matrix of silty sand
size consisting of quartz, chlorite, calcite, musco
vite, epidote and iron oxides. The foliation is
raised by the parallel arrangement of quartz,
plagioclase, lithic fragments, chlorite and musco
vite. The weathered plagioclase grain is partially
kaolinitized and replacement by calcite patches
due to chemical weathering.
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Scanning Electron Microscopy
SEM micrographs of the deteriorate rock inscrip
tions show that the greywacke surface is rough,
porous, crumbling, and fractures have flakes,
scales and etch pits due to alteration and weathering processes (Figure 7A). Mechanical weath
ering effects take place in hot deserts such as
Wadi Hammamat. The absorbed sun heat causes
not only heating of the rock surface but also
external mechanical stress for linear and volume
expansion or contraction of the rock and its
minerals [21]. These stresses are causing many
fissures and flakes in greywacke as seen in SEM
micrographs (Figure 7B). Several rock fragmentsweather and the surfaces can be seen rough, scaled
and flaked as a result of the thermal action. On
the other hand, the action of rain, moisture and
groundwater on the greywackes can cause a diffe
rent expansion and consequently contraction of
minerals upon drying. Between wet and dry zones
a shear force may set up and causes many fractures
both between and within mineral grains. The SEM
micrographs of greywackes show many deep
fissures inside the internal structure and the
opening of the mineral grains boundaries as a
result of water action. Water weathering leads to
changes of the mechanical behaviour and strength
parameters of the rock. The rock strength para
meters were changed by the development of
crack fractures and microfractures due to water
absorption [22].
Pits are also present on the studied samples, with
diameters and depths ranging from macroscopic
to microscopic scales. Secondary minerals such as
chlorite, sericite, kaolinite and calcite typically
cemented the greywackes. With prolonged wet
ting and draying, these secondary minerals beco
me soft and fail readily, creating numerous pits.
For instance, the dissolution and leaching ofcalcite by acidic water lead to the formation of
irregular pores which may be randomly distribu
ted. Moreover, the increase in number and size of
pits in the greywacke is due to the intermineral
space that results from transformed several pri
mary minerals into fine aggregates from secon
dary minerals have total volume less than the
total volume of the primary minerals (Figure 7G).
For instance, several feldspars are pitting as a
result of partially or completely altered to seri
cite (hydromica) and clay minerals, through the
Figure 6(left to right). The examination of the greywacke samples thin section under cross polarised microscope.(A) grey
wacke rock composed mainly of quartz, plagioclase and epidote embedded in pelitic groundmass. (B) Quartz crystals occur
fractures and opening of microfractures. (C) Plagioclase grains dissected by microfaults and partially altered to epidote and
sericite as a result of mechanical and chemical weathering.
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dissolution and leaching processes. Generally the
connected pores and microfracture within grey
wacke minerals act as channels through which
the soluble salts and the alteration products mi
grate and cause many deterioration features in
greywackes. These soluble salts entrapped in thepores, between grains and cover the greywacke
surfaces, often causing microfractures, pores and
fractures. In some weathered greywacke close to
the position of the Portland cement mortars, the
SEM micrographs show that the gypsum salts pre
cipitate in pore spaces and coatings the calcite
grains as a result of chemical processes. Ollier
stated that a thermal and hydration stresses
developed when salts precipitated in the poresand cracks between or in the grains of the rock
[6]. The salt crystals expand and exerts hydra
tion pressure against the pore and crack walls
when hydrates. Ultimately the thermal and hydra
tion processes lead to disintegration of the grey
wacke rock. Sulphates may be coming from the
atmosphere (pollution) or cement mortars.
Interactions between the greywackes and the
atmosphere or adjoining mortars leads to the
formation of gypsum salts, producing damage to
the original structural of greywacke rocks. SEM
micrographs of some greywacke samples adjoining
the cement mortars show crumple of the gypsum
crust and rolled the outer layer of greywacke,
ultimately separated from the rock inscriptions.
Commonly, the salt weathering leads to flaking
and scaling the stone surface [23, 24].
XRay Diffraction Analysis
Four samples of greywacke rock inscriptions were
collected and studied by Xray diffraction to de
termine their mineral composition. The results of
the analyses is shown in Table I. The altered grey
wacke sample from the Hammamat quarry wallconsists of quartz (SiO2), microcline (KALSi3O8),
plagioclase, calcite (CaCO3), halite (NaCl), anhyd
rite (CaSO4), iron oxide nontronite (smectite
group), orthoclase, hematite (Fe2O3), magnetite
(Fe3O4), halloysite, kaolinite (hydrated aluminum
silicate), greenalite (Fe2+, Fe3+) 23 SiO2O5(OH)4,
chloritoid, magnesio chloritoid and forsterite
(Mg2SiO4).
The clay minerals shown in Table I are represented
mainly by nontronite (smectite group) kaolinite
Figure 7 (left to right). The SEM micrographs of external deteriorated greywacke surfaces (rock inscriptions).
(A) The weathered greywacke surfaces are porous and fractures have flakes and scales. (B) Many fissures and flakes of rock
break away from the greywacke surfaces (C) Kaolinite grains and several secondary minerals contain many residual pores
between them.
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and halloysite, commonly dispersed as a result of
chemical alteration of feldspar minerals and ferromagnesian minerals. The clay minerals normally
occur as alteration products, filling the fractures,
microfractures and cleavages. The change of the
moisture content of clay minerals can cause signi
ficant problems related to the high swelling pres
sures such as the opening up of microfractures and
fractures and lead to rock falls. The crystallisation
of soluble salts in pores and cracks between or in
the grains of rock is one of the major causes ofgreywackes decay in nature [25, 26]. Halite and
gypsum accumulation occurs on the faces of the
Hammamat stone inscriptions due to the influence
of meteoric water, condensation, groundwater
and Portland cement. XRD analyses have shown
the predominance of gypsum in their crystalline
phases (gypsum and anhydrite). The accumulation
of gypsum and halite salts behind the rock inscrip
tion surfaces lead to a detachment of the stone
material in the form of granular disintegration,
contour scaling and flaking.
XRay Fluorescence Analysis
Three samples from the altered greywacke rock
inscriptions were collected and analysed by XRF
to determine their elements. The results of this
analysis are listed in Table II.
There are some differences between the chemical
composition of greywacke rocks in amounts of
SiO2, TiO2, MnO, K2O, Fe2O3, Al2O3, CaO, MgO, CaO
and Na2O. These differences may be due to thealteration and deterioration processes. The high
amount of Na2O in greywacke samples is attributed
to the greater amount of Narich plagioclase and
alkali feldspar. The greywacke samples have a
high content of iron oxides due to the mineral
alteration and high content of MgO due to the
high amount of phyllosilicate minerals such as
chlorite, mica and clay minerals. Moreover, the
CaO content is higher in greywacke samples, which
can attributed to the greater amount of Carich
plagioclase, epidote and carbonate minerals.
Sample Material Type Chemical composition
1
Greywacke rock
from Wadi
Hammamat
Quartz (51.65%), Microcline (3.2%), Calcite (5.89%), Halite
(9.66%), Anhydrite (6.25%), Iron oxide (6.76%), Nontronite
(smectite group, 5.58%), Caplagioclase (anor thite, 1.14%),
Epidote (7.39%), and Chloritoid (Brittle mica, 2.48%)
2Quartz (63.65%), orthoclase (14.51%), Hematite (3.63%),
Anhydrite (13.56%), Epidote (4.65%)
3Quartz (62.35%), Microcline (6.01%), Calcite (8.11%),
Magnetite (8.3%), Hematite (11.97%)Chloritoid (3.25%)
4Quartz (53.65 %), Halloysite (4.9%), Kaolinite (hydrated aluminum
silicate) (4.56%), Gypsum (10.46 %), Hematite (4.33%), Greenalite
(Fe2+, Fe3+) 23 SiO2O5 (OH)4 (8.5%), Magnesio chloritoid (5.7%),
Forsterite (Mg2SiO4) (7.9%)
Table I. Results of Xray diffraction analysis of greywacke rocks from Wadi Hammamat.
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Chemical Classification
Different diagrams were constructed to classify
the sedimentary rocks according to the chemical
analysis such those of Pettijohn et al. [27], Crook
[28], and Blattet al. [29].The analysed samples
were plotted using Blatts Ternary diagram [29].
This diagram indicates that the plotted samples
fall in the greywacke field lying close to the Fe2O3
+ MgO field. This is again confirmed by plottingthe samples on the Log (Na2O/K2O) versus Log
(SiO2 /Al2O3) diagram, suggested by Pettijohn et
al. [27], where the studied samples mostly fall in
the greywacke field. Furthermore, the samples
were plotted on the Na2O K2O diagram by Crook
[28] where the all greywacke samples fall in the
quartzintermediate field. Combining the three
diagrams, the greywacke rock inscriptions can be
described as ferromagnesian rich and quartzintermediate greywacke. The chemical classifica
tion diagrams also prove that the greywackes
have a high content of ferromagnesian minerals
such as chlorite, mica, chloritoid (brittle mica),
Magnesio chloritoid and forsterite (Mg2SiO4) as
detected by XRD. The petrographic study suggests
that the groundmass in greywacke consists essen
tially in ferromagnesian minerals and calcite. It
is know that the ferromagnesian minerals were
rapidly altered as a result of chemical processes
and converted into clay minerals.
Degree of Weathering
The degree of chemical weathering for greywacke
rocks can be quantified by applying the Chemical
Index of Alteration (CIA) [15]. The CIA was used
to quantify and to calculate the degree of rock
alteration and deterioration [10]. The CIA can be
obtained by using the following equation:
[Al2O3/ (Al2O3 + CaO* + Na2O + K2O)] 100. If
the CIA value less than 50% it indicates that therock is unweathered. In case the CIA value ranges
between 50% and 75%, it indicates that the rock
have a moderate weathering While if the value if
more than 75% this indicate that the rocks suf
fered strong weathering. The CIA values of the
samples analysed were of 58, 69 and 73, indica
ting a moderate weathering. This index reflects
the chemical alteration of plagioclase, orthoclase,
microcline and mica to kaolinite. Generally, thisindex is used for calculating the total chemical
weathering of greywackes in Wadi Hammamat.
Conclusions
The greywacke rock inscriptions have significantly
deteriorated in the last decades. Several types of
rock deterioration can be found, namely exfolia
tion, flakes, efflorescence, current detachment
of stone material and deformation. The site is
affected by a series of joints, faults, cracking,
SamplesElement Contents (wt %)
SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O Total
1 65.08 0.58 13.25 6.05 0.06 2.51 9.65 2.03 0.75 99.96
64.22 0.70 13.90 6.60 0.15 5.10 4.65 2.62 0.98 98.92
66.69 0.82 14.50 2.95 0.10 2.12 6.17 4.70 1.19 99.24
2
3
Table I. Results of Xray diffraction analysis of greywacke rocks from Wadi Hammamat.
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sliding movements, dislocation block and rock
falls. It is worth mentioning that the fall down of
the stone blocks leads to the damage of manyrock inscriptions carving on greywacke rocks.
Furthermore, two types of the failure might result
from thermal weathering (insolation weathering),
including exfoliation and disintegration of the
stone. In addition, water from rainwater, moisture
and groundwater assist in the weathering of
greywacke minerals, increasing the chemical
weathering and leading to the formation of clay
minerals. The petrographic analysis reveals that
all the greywacke rocks are mainly cementing by
calcite, iron oxides, sericite, chlorite and clay
minerals. The ferromagnesian (chlorite, chlori
toid, magnesio chloritoid and forsterite), iron
oxide, calcite and clay minerals were easily al
tered and removed by chemical weathering. With
increasing grade of the chemical weathering by
the dissolution of calcite and clay minerals the
amount of microfractures and voids increases in
the greywacke rocks and causing damage of therock inscriptions. The XRF analysis reveals that
the greywackes have a high content of Fe2O3 due
to the alteration processes and the high content
of MgO due to the high amount of ferromagnesian
minerals. Gypsum, anhydrite and halite were the
common salts developing in the greywacke rock
inscriptions. High gypsum content near the sur
face is a crucial factor for flaking, pitting and
contour scaling, when the areas with high load ofhalite are characterised by a visibly darker weak
surface. Gypsum and anhydrite formation cause
damage of the Portland cement mortars and
their adjoining rock inscriptions. The reaction
between the cement mortar and the greywackes
will eventually lead to flake, crumble and deterio
rate greywacke rocks. The chemical classification
diagrams confirmed that the greywacke rock can
be described as ferromagnesian rich quartzinter
mediate and have a high content of ferromagne
sian minerals as detected from petrographic
studied, XRD and XRF analysis . These minerals
are easily altered and finally transformed into
clay minerals and cause intensive disintegration
of greywacke rock inscriptions. Moreover, the CIA
values of the analysed greywacke samples indica
ted a moderate to less strong weathering. Conse
quently, we believe that the temperature change,
moisture, rain, salts, and incorrect restoration
representing the very important factors lead to
the disintegration of greywacke rocks.
Geochemically, the greywacke deter ioration can
be attributed to the dissolution of calcite, clay
and iron oxides. Feldspar and ferromagnesian
minerals by intensive alteration were easily remo
ved, altered into iron oxides and clay minerals
very rapidly and cause different deterioration
features in the greywacke rock inscriptions.
Acknowledgments
The author wishes to thank Dr. Mohamed Fathy,geology in the laboratory of Egyptian Geological
Survey in Cairo for his helping during laboratory
work. This work has been supported by the High
Institute of Tourism and Restoration,
AlexandriaEgypt.
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HESHAM ABBAS KMALLY
Conservation scientist
Contact: [email protected]
Hesham Kmally is a conservation scientist
specialised in conservation of rock inscriptions.He obtained his Master degree in Geochemistry,
Petrography and Structural Studies of Rocks from
South Valley University, Egypt in 1999. He was
director of the Conservation Center at the Nubia
Museum in Alexandria, Egypt up to 2003, after
which he pursued a PhD in Archaeological Quar
rying and Conservation of Rock Inscriptions in
Aswan from the same university in 2005. He now
works at the Conservation Department of the
High Institute of Tourism, Hotel Management
and Restoration, Egypt.
DETERIORATION OF ROCK INSCRIPTIONS IN EGYPT
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