Abbas, H. Deterioration Rock Inscriptions Egypt. 2011

8/3/2019 Abbas, H. Deterioration Rock Inscriptions Egypt. 2011

1/15

e-conservationthe online magazine No. 21, September 2011


2/15

DETERIORATION AND

RATES OFWEATHERING

OF THE MONUMENTAL

ROCK INSCRIPTIONS AT

WADI HAMMAMAT,

EGYPT

By Hesham Abbas Kmally


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.
http://www.e-conservationline.com/


4/15

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

68 econservation

HESHAM ABBAS KMALLY

Figure 1. Example of rock inscriptions from Wadi Hammamat.

Figure 2. Roman stone watchtowers on the top of hills.


5/15

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.



6/15

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

70 econservation

HESHAM ABBAS KMALLY


7/15

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.

econservation 71



8/15

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.

72 econservation

HESHAM ABBAS KMALLY


9/15

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.

econservation 73



10/15

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.

HESHAM ABBAS KMALLY

74 econservation


11/15

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.


econservation 75


12/15

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.

HESHAM ABBAS KMALLY

76 econservation


13/15

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.

References

[1] M.K. Akaad, and A.M. Nowier, Geology and

lithostratigraphy of the Arabian Desert Orogenic

Belt of Egypt between Latitudes 25 30' and 26 30'

N, Bulletin of the Institute of Applied Geology4(3),

King Abdul Aziz University, Jeddah, 1980, pp.

127134

[2] M.K. Akaad, and A.M. Nowier., Lithostrati

graphy of the Hammamat Um Seleimat district,

Eastern Desert, Egypt, Nature 223, 1969, pp.

284285


econservation 77


14/15

[3] B. Grothaus, D. Eppler and R. Ehrlich, Deposi

tional environment and structural implication of

the Hammamat formation, Annals of the Geolo

gical Survey of Egypt9, 1979, pp. 564590

[4] M. Ghanem, A.A. Dardir, M.H. Francis, A.A.

Zalata, and K.M. Abu Zeid, Basement rocks in

Eastern Desert of Egypt north of latitude 1640'N,

Annals of the Geological Survey of Egypt3, 1973

[5] A.E.A. Ahmed, M.L. Kabesh, and S.G. Mawas,

Dokhan Volcanics of Abu Gawa area and their

epiclastic derivatives Central Eastern Desert,

Egypt, Bulletin of the Faculty of Science, Assiut

University17, 1988, pp. 195222

[6] C.D. Ollier, Weathering, Longman, New York,

1984

[7] G. Benito, M. J. Machado and C. Sancho, Sand

stone weathering processes damaging prehistoric

rock paintings at the Albarracin Cultural Park, NESpain, Environmental Geology22(1), 1993, pp.

7179, doi:10.1007/BF00775287

[8] M.J. Selby, Earth's changing surface. An intro

duction to Geomorphology, Oxford University Press,

Oxford, 1985

[9] L.P. Zhu, J.C. Wang, and B.Y. Li, The impact

of solar radiation upon rock weathering at lowtemperature: A laboratory study, Permafrost

and Periglacial Processes 14, 2003, pp. 6167,

doi: 10.1002/ppp.440

[10] H.W. Nesbitt, and G.M. Young, Early Prote

rozoic climates and plate motions inferred from

major element chemistry of lutites, Nature 299,

1982, pp. 715717

[11] J.R. Price, M.A.Velbel, Chemical weather

ing indices applied to weathering profiles develo

ped on heterogeneous felsic metamorphic parent

rocks, Chemical Geology202, 2003, pp. 397416

[12] Z. Jin, J. Cao, J. Wu and S. Wang, A Rb/Sr

record of catchment weathering response to

Holocene climate change in Inner Mongolia,

Earth Surface Processes and Landforms 31, 2006,

pp. 285291, doi: 10.1002/esp.1243

[13] S.L. Yang, F. Ding, Z.L. Ding., Pleistocene

chemical weathering history of Asian arid and

semiarid regions recorded in loess deposits of

China and Tajikistan, Geochimica et Cosmochi

mica Acta 70, 2006, pp. 16951709,

doi:10.1016/j.gca.2005.12.012

[14] S. Ceryan, New Chemical Weathering Indices

for Estimating the Mechanical Properties of Rocks:

A Case Study from the Krtn Granodiorite, NE

Turkey, Turkish Journal of Earth Sciences 17, 2008,

pp. 187207

[15] D.E. Kirkwood, H.W. Nesbitt, Formation and

evolution of soils from an acidified watershed:

Plastic Lake, Ontario, Canada, Geochimica et

Cosmochimica Acta 55, 1991, pp. 12951308,

doi: 10.1016/00167037(91)90308R

[16] V. Fassina, Atmospheric pollutants respon

sible for stone decay. Wet and dry surface deposi

tion of air pollutants on stone and the formationof black scabs, in F. Zezza (ed.), Weathering and

Air pollution, First Course, Community of Mediter

ranean Universities, University School of Monu

ment Conservation, Mario Adda Editore, Bari,

1991, pp. 6786

[17] M.B. Ismaiel, Geoarchaeological Study on

Rock Art Sites, with Special Emphasis on Gebel

ElSilsilah and Wadi Hammamat, Qena 7(2),

Faculty of Arts South Valley University, 1996,

pp. 759

HESHAM ABBAS KMALLY

78 econservation
http://dx.doi.org/10.1007/BF00775287http://www.e-conservationline.com/http://dx.doi.org/10.1002/esp.1243http://dx.doi.org/10.1016/0016-7037(91)90308-Rhttp://dx.doi.org/10.1002/ppp.440


15/15

[18] A.A. Abdel Monein, Overview of the geomor

phological and hydrogeological characteristics of

the Eastern Desert of Egypt, Hydrogeology Journal

13(2), 2005, pp. 416425, doi:10.1007/s10040

0040364y

[19] K.I. Meiklejohn, Aspects of the weathering of

the Clarens formation in the KwazuluNatal drakens

berg. Implications for the preservation of indige

nous rock art, PhD Thesis, University of Natal,

Pietermaritzburg, 1995, unpublished

[20] F.G. Bell, Engineering properties of soils and

rocks, Butterworths, London, 1983

[21] S.M. Soliman, Thermal weathering of sedimen

tary ancient monuments, Department of Geology,

Ain Shams University, Cairo, Egypt, 1999

[22] P. A. Rebinder, L. A. Shreiner, K. F. Zhigach,

Hardness reducers in drilling: a physicochemical

method of facilitating the mechanical destructionof rocks during drilling, Council for Scientific and

Industrial Research, 1948

[23] D.A. Robinson, and R.B.G. Williams, (eds),

Rock Art and Landform Evolution, John Wiley and

Sons, Chichester, 1994

[24] S. Hoerle, A preliminary study of the weath

ering activity at the rock art site of Game passshelter(KwazuluNatal) in relation to its conserva

tion, South African Journal of Geology108(2),

2005, pp. 297308, doi: 10.2113/108.2.297

[25] I.S. Evans, Salt crystallisation and weath

ering: a review, Revue de Geomorphologie Dyna

mique 19, 1970, pp. 15377

[26] E.M. Winkler, and P.C. Singer, Crystallisation

pressure of salts in stone and concrete, Geological

Society of America Bulletin 83, 1972, pp. 35093514

[27] F.J. Pettijohn, P.E. Potter, R. Siever, Sand

and Sandstone, SpringerVerlag, New York, 1972

[28] K.A.W. Crook, Lithogenesis and geotectonios:

the significance of compositional variations in

flysch arenites (greywackes), in R.H. Doti, and

R. H. Shaver (eds.), Modem and Ancient Geosyn

clinal Sedimentation, Society of Economic Paleon

tologists and Mineralogists Spec. Publ. 19, 1974,

pp. 304310

[29] H. Blatt, G.V. Middleton, R.C. Murray, Origin

of Sedimentary Rocks, PrenticeHall, 1980

[30] W.F. Hume, Geology of Egypt, Vol. 2, Part I.

The Metamorphic Rocks, Geological Survey of

Egypt, 1934

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.


econservation 79
http://www.e-conservationline.com/http://dx.doi.org/10.2113/108.2.297http://dx.doi.org/10.1007/s10040-004-0364-yhttp://dx.doi.org/10.1007/s10040-004-0364-y

Abbas, H. Deterioration Rock Inscriptions Egypt. 2011

Documents

Transcript of Abbas, H. Deterioration Rock Inscriptions Egypt. 2011