Vol.3, No.10, 895-905 (2011) Natural Science
Copyright © 2011 SciRes. OPEN ACCESS
Natural radioactivity and the resulting radiation doses in
some kinds of commercially marble collected from
different quarries and factories in Egypt
S. Fares1*, Ali. A. M. Yassene1, A. Ashour1, M. K. Abu-Assy2,
M. Abd El-Rahman1
1Department of Radiation Physics, National Center of Radiation Research and Technology NCRRT, Atomic Energy Authority, Cairo,
Egypt; *Corresponding Author: sfares2@yahoo.com
2Physics Department, Faculty of Science, Suez-Canal University, Ismailia, Egypt.
Received 21 August 2011; revised 27 September 2011; accepted 5 October 2011.
Fourteen samples of marble were collected from
different factories in Egypt. The samples were
crushed, dried in controlled furnace for around
twenty four hours, and then stored for five weeks
in plastic Marinelli beakers. Concentrations and
the U- and Th-bearing minerals were studied by
scanning electron microscopy (SEM) and energy
dispersive X-ray spectrometry (EDS).The gamma
radiation of the samples was measured, employ-
ing high resolution γ-ray spectroscopy with an
accumulating time for about 80000 sec. each.
From the measured γ-ray spectra, activity con-
centrations were determined for marble samples
226Ra (37. 6 ± 1.7 - 100.54 ± 3.2 Bq/kg), 232Th (3.57
± 0.64 - 9.37 ± 1.80 Bq/kg) and 40K (30.68 ± 1.1 -
1196 ± 4.9 Bq/kg). The absorbed dose rates,
annual effective dose rates, radium equivalent
activities as well as the radiation hazard indices
were estimated. The radium equivalent activities
(Raeq) are lower than the limit of 370 Bq·kg1 set
by the Organization for Economic Cooperation
and Development (Exposure to radiation from
the natural radioactivity in building materials.
Report by a Group of Experts of the OECD,
Nuclear Energy Agency, OECD, Paris, 1979) [1].
All obtained results referred to the fact that all
the concentrations were within the allowed
limits to domestic use. Comparing the results in
this work with those published by International
Atomic Energy Agency and local and universal
researches, it was found that these concentra-
tions were within the allowed limits for agricul-
tural and domestic uses.
Keywords: Marble; Effective Dose; External and
Internal Hazard Indexes; NORMS; Gamma
Spectrometry; Radium Equivalent.
Radionuclides in our environment are of three general
types: primordial, cosmogenic, and anthropogenic (man-
made). Natural radionuclides are present in all rocks in
varying amounts depending on their concentration levels
in source rock materials. It is known that the radionuclides
238U, 235U and 232Th may become incorporated in igneous
materials when they are originally formed from the
molten state.
The use of building materials rich in gamma-emitting
primordial radionuclides may cause substantial exposures
to those inhabiting dwellings built with these products.
The main products of concern are building stones,
concrete, plaster and industrial by-products and residues
used as ballast in building materials. The background
levels in rocks from the 238U and 232Th series and 40K
make similar contributions to the externally incident
gamma radiation as the median concentrations of 238U,
232Th and 40K in the earth s crust, and are typically
around 35, 30 and 400 Bq/kg respectively. The use of
these building materials is mostly used for floors and
therefore assessment of exposure should be based on
scenarios where the material is used in a typical way.
Natural building stones are made from different types
of material. The radionuclide content is lowest in basic
rocks of magmatic origin. Also marbles, limestone and
various detrital sedimentary rocks contain only small
amounts of natural radionuclides. Higher concentrations
are generally found in acid magmatic rocks, especially in
late-magmatic granites, and in some metamorphic rocks.
In minerals the incorporation of uranium and thorium
into the crystal lattice depends on the abundance of these
elements in the rock during crystallization and on the
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
matching of the chemical properties and the atomic radii
of hosts and substitutes. Based on these general expecta-
tions the ratio of the uranium or thorium contents of
individual minerals should be more or less constant. The
absolute concentrations of uranium and thorium in the
minerals should be related to the geochemical charac-
teristics of the rock from which the detrital grains origi-
nate, and give an indication of their provenance [2] .
Marbles show variety of textures on account of exist-
ing minerals & re-crystallization patterns. Texture depends
upon form, size, and uniformity of grain arrangements.
Marbles can be classified on the basis of the following
1) Calcite Marble—Mostly CaCo3; MgCo3 < 0.50%
2) Dolomite Marble—Having > 40% MgCo3.
3) Magnesium Marble—MgCo3 between 5% to 40%.
4) Serpentine Marble-remobilised marble due to the
effect of thermodynamic metamorphic wherein serpentine
is prominent.
5) Onyx Marble—Lime carbonate deposition on account
of cold water solution activity.
The major mineral impurities in marble (Quartz,
Tremolite Actinolite, Chert, Garnet, Biotite, Muscovite,
Microline, Talc, Fosterite. While the major chemical
impurities in marble (SiO2, Fe2O3, 2Fe2O3, 3H2O, Li-
monite, Manganese, Al2O3·FeS2 (pyrite). On account of
the mineral composition of marble the color variations.
All building materials including marble contain various
amounts of natural radioactive nuclides. Materials derived
from rock and soil contain mainly natural radionuclides
of the uranium 238U and thorium 232Th series as well as
potassium 40K. Marbles, in particular, exhibit an enhanced
elemental concentration of these natural radionuclides in
comparison to the very low abundance of these elements
observed in the mantle and the crust of the Earth. The
igneous rocks of marble composition are strongly
enriched in U and Th (on an average 5 ppm of U and 15
ppm of Th), compared with rocks of basaltic or
ultramafic composition (<1 ppm of U) [3-5]. In the 238U
series, the decay chain segment starting from radium
(226Ra) is radiologically the most important and therefore
reference is often made to 226Ra instead of 238U. The
worldwide average concentrations of 226Ra, 232Th and
40K in the earth’s crust are about (50, 50 and 500) Bq
kg–1, respectively [6,7].
The presence of the radioisotopes in materials causes
external exposure to the people who live in the building.
226Ra and 232Th can also increase the concentration of
222Rn and 220Rn and of its daughters in the building. 40K
and part of the above-mentioned radionuclides cause
external exposure while the inhalation of 22 2 Rn, 220Rn
and their short lived progeny leads to internal exposure
of the respiratory tract to alpha particles [8,9]. Any
beneficial practices involving the use of radioactive
materials obviously give rise to radioactive waste that,
by definition, should be viewed as one aspect of the
In the world, many rich marble deposits in countries
like Portugal, Spain, Italy, Greece, Turkey, Iran and
Pakistan are located in Alpine-Himalayan belt. As a result
of its geological location, Egypt possesses very rich,
natural stone reserves in various colors and patterns.
Currently, Egypt has about 500 marble and granite
factories. According to specialists in the industry, there
are 3 types of factories: factories that are just involved in
cutting the blocks into plates of marble and then
distributing them to workshops that handle further
cutting and polishing, factories that cut and polish the
plates, and factories that do the whole process until the
final product is produced. The area of “Shak El Thoban”
in Katameyya has become a conglomeration of factories
working in the marble and granite industry. This area
was first occupied by quarrymen quarrying the limestone
in the hills and mountains of Katameyya.
In order to be able to assess radiological risk, it is
important to study the levels of radiation emitted from
building materials. In this context, the present work aims
at determining the specific activities (in Bq·kg1) of
226Ra, 232Th and 40K in some Marble samples of wide use
locally. In order to estimate their radiological effects, the
total absorbed dose rate (D), the radium equivalent
(Raeq), the external hazard index (Hex) and the internal
hazard index (Hin) have been estimated. Due to the health
risks associated with the exposure to indoor radiation,
many governmental and international bodies such as the
International Commission on Radiological Protection
[10], the World Health Organization, etc. have adopted
strong measures aimed at minimizing such exposures.
Hence, this work is important from both health and
science perspectives. Even though the work cannot cover
all the building material samples in Egypt, it can be a
pointer for similar works if the findings are significant. It
may also help adopt policies with respect to regulating
the use of building materials that might be of risk to
public. Authorities in areas such as Minister of Com-
merce and Industry and the Egypt Standards Organiza-
tion can benefit from the outcome of this project.
2.1. Samples Collection and Preparation
A total of 14 different sample of marble tiles used in
constructing houses and other buildings, were collected
from different location in Egypt. These tiles, are widely
used as building and ornamental materials. The samples
were crushed and homogenized in grinders at the labo-
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
ratory. They were then sieved through a 40-mesh sieve
and then heated at 110˚C in an oven for 24 h to get rid of
moisture if any. The samples were then cooled and
transferred to plastic Marinelli beakers of volume 500 ml
each and then properly sealed so as to keep the 222Rn gas
that emanate from the crushed samples to be confined to
the beaker, as much as possible. The sealed Marinelli
beakers were then kept for a period of 1 month to allow
the short-lived progenies of 226Ra and 232Th to reach
secular equilibrium. The radioactivity concentrations of
226Ra, 232Th and 40K in all of them were then determined.
Fourteen samples of marble from locations were collected
from different factories in Egypt. 14 samples of Marble
(8 sample from Sinai, 3 sample from Suez Golf, 2 sam-
ple from Upper Egypt and one sample from Red Sea)
where collected from different places in (A.R.E) as
shown in Figure 1.
2.2. Mineralogical Study
The 14 kinds of marble used in this study are the most
popular types, according to the factories that provided
the samples. Selected thin sections of fresh rocks were
examined by petrographic and scanning electron mi-
croscopy {SEM micrographs were obtained with a JSM-
5400 (Jeol/Japan)}. Fracture surfaces were obtained by
compression of the specimens. Surface of fracture was
sputtered with thin layer of gold. Minerals were ana-
lyzed by Energy Dispersive Spectrometry (EDS) at Na-
tional Center of Radiation Research and Technology
NCRRT, Atomic Energy Authority, Cairo, Egypt. For
XRD analysis, X-Ray Diffraction patterns were ob-
tained with XRD—DI series, Shimadzu apparatus using
Ni—filter and Cu—K target.
2.3. Gamma Spectrometric Analysis
The HPGe detector had a relative efficiency of 30%
and full width at half maximum (FWHM) of 1.89 keV
for the 1332 keV γ-ray line of 60Co. The detector was
surrounded by a special heavy lead shield of about 10
cm thickness with inside dimensions 28 cm diameter
40.5 cm high to reduce background radiation originating
from building materials and cosmic rays. The spectro-
meter was calibrated using both uranium nitrate source
and potassium chloride standard sources in the same
geometry as the samples. A set of high quality certified
reference materials (IAEA, RG-set) was used. The
analysis of output spectrum was carried out with the help
of Canberra Genie 2000 software version 3.0.
Figure 1. Location of marble quarries and factories in Egypt.
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
The 226Ra activities (or 238U activities for samples as-
sumed to be in radioactive equilibrium) were estimated
from 214Pb (351.9 keV), 214Bi (609.3, 1764.5 keV) and
226Ra (185.99 KeV). Several 214Pb and 214Bi peaks were
also monitored. The Gamma ray energies of 212Pb (238.6
keV) and 228Ac (338.4, 911.07, 968.90 keV) were used
to estimate the concentration of 232Th. The natural
abundance of 235U is only 0.72% of the total uranium
content and hence was not considered in the present
study. The activity concentrations of 40K were measured
directly by its own gamma rays (1460.8 keV). The activ-
ity concentrations were calculated from the intensity of
each line taking into account the mass of the sample, the
branching ratios of the γ-decay, the time of counting and
the efficiencies of the detector. The activity concentra-
tions of the investigated samples were calculated from
EiEiEd s
AN tM
where NEi is the Net Peak Area of a peak at energy Ε, εE
is the detection efficiency at energy Ε, t is the counting
lifetime, γd is the number of gammas per disintegration
of this nuclide for a transition at energy E, and Ms is the
mass in kg of the measured sample. If there is more than
one peak in the energy analysis range for a nuclide, then
an attempt to average the peak activities is made. The
result is then the weighted average nuclide activity. The
correction for the contribution of 232Th via its daughter
nuclide 228Ac (1459.2 keV peak) to the 1460.8 keV peak
of 40K was made according to [11]
The error in
40 %9.3
Th K
K activityAA (2)
Activity concentrations, calculated from the intensity
of several γ-rays emitted by a nuclide, are grouped to-
gether to produce a weighted average activity per nu-
clide. Errors arise due to a number of factors, like effi-
ciency calibrations, peak area determination and random
uncertainties associated with background and sample
counts. Each sample was measured during an accumu-
lating time between 20 and 24 h in the Laboratory of
Atomic and Nuclear Physics, Department of Physics,
Suez Canal University. After each sample counting, an
empty cylindrical plastic container was placed in the
detection system, during a counting period of 24 h, in
order to collect the background count rates.
2.4. Assessment of Radiological Risk
In order to assess the radiological impact of marble
used as building materials, the model of a rectangular
parallel lepipedon house building( 3 m × 3 m × 3 m),
with infinite thin walls and no doors and windows
(standard room model) was commonly considered [6].
The absorbed gamma dose rate in air 1m above the
ground surface for the uniform distribution of radionu-
clides (238U, 232Th and 40K) was computed on the basis
of guidelines provided by UNSCEAR (1993, 2000) [6,7].
The conversion factors used to compute absorbed ga-
mma dose rate (D)in air per unit activity concentration in
(1 Bq·kg–1) samples correspond to 0.621 nGyh–1 for 232Th,
0.462 nGyh–1 for 238U, and 0.0417nGyh–1 for 40K [12]:
D = (0.621 ATh + 0.462 ARa + 0.0417 AK ) nGy·h–1 (3)
where, ATh, ARa and AK represent the average activity
concentrations of 232Th ,226Ra and 40K in Bq·kg–1, respec-
Finally, in order to make a rough estimate for the an-
nual effective dose outdoors, one has to take into account
the conversion coefficient from absorbed dose in air to
effective dose and the outdoor occupancy factor. In the
UNSCEAR recent reports [6,7], the Committee used 0.7
Sv·Gy1 for the conversion coefficient from absorbed
dose in air to effective dose received by adults, and 0.2
for the outdoor occupancy factor. Annual effective dose
rate outdoors in units of μSv per year is calculated by the
following formula:
AEDR (Indoor) = dose rate (in nGy·h1) × 24 h
× 365.25 d × 0.8
× 0.7 SvGy1 × 106 (4)
AEDR (Outdoor) = dose rate (in nGy·h1) × 24 h
× 365.25 d × 0.2
× 0.7 SvGy1 × 106 (5)
According to most recent regulations and especially
the recommendation No. 112 issued by the European
Union in 1999 [13], building materials should be ex-
empted from all restrictions concerning their radioactive-
ity, if the excessive gamma radiation due to those mate-
rials causes the increase of the annual effective dose
received by an individual by a maximum value of 0.3
mSv. Effective doses exceeding the dose criterion of 1
mSv · y1 should be taken into account in terms of radia-
tion protection. It is therefore recommended that controls
should be based on a dose range of 0.3 - 1.0 mSv·y1,
which is the building material gamma dose contribution
to the dose received outdoors.
Marbles are widely used in the building construction
that includes tiling, ornamental and covering both for
exterior and interior use. In order to assess the radiation
hazard associated with the building materials used, the
Raeq have been evaluated, where it is assumed that all
the decay products of 226Ra and 232Th are in radioactive
equilibrium with their precursors. The Raeq is calculated
according to the following formula [14,15]:
Raeq = ARa 1.43 + ATh + 0.077 AK (6)
where ARa, ATh and AK are The activity concentrations
(Bq·kg1) of 226 Ra, 232Th and 40K, respectively. This
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
formula is based on the estimation that 1 Bq·kg1 of 238U,
0.7 Bq·kg1 of 232Th and 13 Bq·kg1 of 40K produce the
same gamma-ray dose rates.
To estimate the gamma-radiation dose expected to be
delivered externally from building materials, a model
was suggested by various researchers to limit the radia-
tion dose from building materials to 1.5 mSv·y1. In this
model the external hazard index has been defined (Hex)
defined by some workers [15,16]:
Hex= ARa/370 + ATh/259 + AK/4810 (7)
The radiation risk is negligible when the maximum
value of the external hazard index is less than unity (Hex
1), which is equivalent to a maximum value of the
Raeq activity < 370 Bq·kg1. In terms of dose equivalent,
this index must be less than unity so that the annual ef-
fective dose due to radioactivity in the material will be
1.5 mSv·y1.
Internal exposures arise from the inhalation of radon
(222Rn) gas and its short-lived decay products as well as
from the inhalation or ingestion of other radionuclides.
Radon is part of the radioactive series of 238U, which is
present in building materials. To assess the internal ex-
posure to 222Rn gas, the internal hazard index has been
defined as [15]:
Hin =ARa/370 + ATh/259+AK/4810 (8)
The use of a material in the construction of dwellings
is considered safe when the maximum value of the in-
ternal hazard index is less than unity (Hin 1), As the
marble are widely used as building and covering materi-
als, it is also possible to use an activity utilization index,
proposed by [7 and/or 13], that facilitates the derivation
of dose rates in air from different combinations of these
three radio nuclides [17].
According to the EC, the following gamma activity
concentration index (Iγr) (representative level index) is
derived for identifying whether a dose criterion is met:
Iγr = ARa/150 + ATh/100 + AK/15 00 (9)
The index Iγr is correlated with the annual dose due to
the excess external gamma radiation caused by superfi-
cial material. Values of index I 1 correspond to 0.3
mSv/y, while I 3 correspond to 1 mSv/y. Thus, the
activity concentration index should be used only as a
screening tool for identifying materials which might be
of concern to be used as covering material. According to
this dose criterion, materials with I 3 should be
avoided, since these values correspond to dose rates
higher than 1 mSv/y [13] which is the highest value of
dose rate in air recommended for population [6,7].
Due to radon inhalation originating from building
materials [13]. The alpha index was determined using
the following formula:
Iα = ARa/200 (Bq·kg1) (10)
where ARa (Bq·kg1) is the activity concentration of 226Ra
assumed in equilibrium with 238U. The recommended
exemption and upper level of 226Ra activity concentra-
tions in building materials are 100 and 200 Bq·kg1, re-
spectively, as suggested by ICRP [10]. These considera-
tions are reflected in the alpha index. The recommended
upper limit concentration of 226Ra is 200 Bq·kg1, for
which Iα = 1.
Table 1 presents the various226Ra, 232Th and 40K ac-
tivity concentrations and their associated absorbed dose
rates and annual effective dose rates for the 14 Marble
samples under investigation. The radioactivity concen-
tration values in the selected Marble samples ranged
from (3.57 ± 0.64) to (9.37 ± 1.8) Bq·kg1 for 232Th,
(37.6 ± 1.7) to (100.54 ± 3.2) Bq·kg1 for 226Ra and
(30.68 ± 1.1) to (1196 ± 4.9) Bq·kg1 for 40K. It was
clearly evident that 40K always contributed to the most
specific activity compared with 232Th and 226Ra. The
sample M14 presented the lowest activity concentrations
for 232Th and 226Ra, whereas it presented the highest ac-
tivity value for 40K. All samples have 40K activity con-
centrations lower than the regular soil values, except
sample M14 with activity concentrations higher than
double those of the regular soil values of 1196 Bq/Kg.
Moreover samples M4, M8 and M9 have 226Ra, active-
ity concentrations higher more than double those of the
regular soil concentrations. The measured minimum,
maximum and mean activity concentration values, to-
gether with the statistical uncertainty (1σ) and standard
deviation (SD), of the above natural radionuclides are
presented for the different regions in Table 1. Figure 2
shows a comparison of concentration for 226Ra, 232Th
and 40K (Bq·kg1).
Figure 2. Histogram comparing the activity concentration
226Ra, 232Th and 40K.
S. Fares et al. / Natural Science 3 (2011) 895-905
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Table 1. 226Ra, 232Th and 40K activity concentrations (Bq·kg1), absorbed dose rate (nGy·h1) and annual effective dose rate (indoor-
outdoor) (mSv·y1) for different marble samples.
Sample name Region
Absorbed Dose Rate D
AEDR (outdoor)
AEDR (indoor)
M1 Suez Golf 39.86 ± 3.1 5.94 ± 0.5 38.16 ± 1.3 23.70 0.03 0.12
M2 Sinai 39.10 ± 1.5 5.52 ± 1.2 53.04 ± 0.9 23.71 0.03 0.12
M3 Sinai 43.03 ± 2.8 8.85 ± 1.9 286.68 ± 0.537.33 0.05 0.18
M4 Suez Golf 100.54 ± 3.2 5.24 ± 1.4 37.56 ± 1.5 51.27 0.06 0.25
M5 Suez Golf 37.6 ± 1.7 4.36 ± 1.02 33.4 ± 2.1 21.47 0.03 0.11
M6 Sinai 54.47 ± 3.9 5.6 ± 1.11 33.8 ± 1.4 30.05 0.04 0.15
M7 Sinai 37.76 ± 1.6 5.97 ± 1.3 43.28 ± 0.7 22.96 0.03 0.11
M8 Sinai 96.46 ± 4.4 6.88 ± 1.21 57 ± 1.3 51.21 0.06 0.25
M9 Red Sea 79.99 ± 2.1 5.03 ± 0.84 34.12 ± 1.5 41.50 0.05 0.20
M10 Sinai 62.51 ± 2.5 7.53 ± 0.93 30.68 ± 1.1 34.85 0.04 0.17
M11 Sinai 40.15 ± 3.5 3.91 ± 0.95 40.8 ± 1.4 22.68 0.03 0.11
M12 Sinai 76.49 ± 1.3 9.37 ± 1.80 47.4 ± 1.7 43.13 0.05 0.21
M13 Aswan 42.66 ± 1.1 3.57 ± 0.64 66.92 ± 2.8 24.72 0.03 0.12
M14 Qena 44.26 ± 2.3 5.57 ± 1.50 1196 ± 4.9 73.78 0.09 0.36
Average Average 56.78 ± 2.5 5.95 ± 1.2 142.8 ± 1.7 35.88 0.044 0.18
Regular soil
(global scale)*
Regular soil
(global scale) 35 30 400 55 0.3 - 1.0 0.3 - 1.0
*Regular Soil (global scale) from UNSCEAR(2000).
The absorbed dose rates (D) indoor air calculated
from the measured activities in marble samples are also
given in Table 1. For the different marble types and the
regions from where they were collected. The absorbed
dose rates indoor air were found to vary from 21.47 to
73.78 nGy·h1 with a mean value of 35.88 nGy·h1.
Average absorbed dose rates for all samples are lower
than the world average value of 55 nGy/h [7], except for
M14 sample. Studies indicate an average outdoor ter-
restrial gamma dose rate of 60 nGy/h in the world rang-
ing from 10 to 200 nGy/h [18]. From the present work
we found that the average terrestrial gamma dose rate is
35.88 nGy/h which is lower than the world average.
The calculated AEDR (outdoor and indoor) values are
given in Table 1. The minimum, the maximum and the
average values for outdoor are 0.03 mSv/y, 0.09 mSv/y
and 0.044 mSv/y, respectively and the corresponding
indoor values are 0.11 mSv/y, 0.36 mSv/y and 0.18
mSv/y respectively.
The Raeq is related to the external gamma dose and
the internal dose due to radon and its daughters [15]. In
the present work, Raeq was estimated for the investi-
gated samples and are given in Table 2. The highest
value of radium equivalent in marble is 144.32 (Bq/kg).
It is observed that the calculated radium equivalent for
all samples are lower than the recommended maximum
value 370 Bq/kg. As reference The world average per-
missible dose limit for public which is recommended by
ICRP [10] is 1.5 mSv·y1 which equivalent to 370
The values of the (Hex, Hin) indices must be less than
unity for the radiation risk to be negligible [16]. For the
maximum value of Hex to be less than unity, the maxi-
mum value of Raeq must be less than 370 Bq/kg. This is
the radiation exposure due to the radioactivity from a
construction material, limited to 1.5 mGyyr1. The
maximum values of Hin equal to unity corresponds to
the upper limit of Raeq (370 Bq·kg1). The values of Hex
for the studied marble samples range from 0.13 to 0.39,
with an average value of 0.21, are less than unity, Table 2.
The mean internal radiation hazard index Hin is for the
studied marble samples is 0.36 (Table 2). The external
and internal radiation hazard indices are less then 1,
which means it is safe for human to carry out their ac-
tivities in the area.
The mean values of Iγ calculated from the measured
activity concentrations of 226Ra, 232Th and 40K are pre-
sented in Table 2 for different marble types and the re-
gions from where they were collected. The calculated
values of (Iγ) for the studied samples varied in the range
between 0.32 - 1.15 for marble types are lower than the
unity (except for M14), Iγ < 1 corresponds to a dose
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
creation of 1 mSv·y1, while Iγ < 0.5 corresponds to 0.3
mSv · y1. It is clear form in Table 2 that the mean value
of the activity index Iγ is 0.53, which is less than the up-
per limit for Iγ < 0.5. The mean computed Iα values for
the studied samples are given in Table 2 for the different
marble sample and the regions where they were col-
lected. The values of Iα ranged from (0.19 to 0.5), with
the mean value of 0.28 for the safe use of a material in
the construction of dwellings, Iα should be less than
Table 3 compares the reported values of natural ra-
dioactivity for marble obtained in other published data
with those determined in this study. As shown in this
table, the radioactivity in marble samples varied from
one country to another. It is important to point out that
these values were not the representative values for the
countries mentioned but for the regions from where the
samples were collected. The values of the radionuclides
concentration for all the selected marble samples in pre-
sent study were in the same range of the corresponding
material in other published data except in some samples.
As shown in Table 3 the values of radium equivalent
obtained for present materials are found to be higher
compared to that of other countries.
Table 2. Calculated raeq (Bq·kg1), Hex and Hin indices, gamma alpha indices (Iγ, Iα) for marble samples.
Sample name Raeq (Bq·kg1) Hin Hex I
γ < 1 Iα < 1
M1 51.30 0.25 0.14 0.35 0.20
M2 51.08 0.24 0.14 0.35 0.20
M3 77.76 0.33 0.21 0.57 0.22
M4 110.93 0.57 0.30 0.75 0.50
M5 46.41 0.23 0.13 0.32 0.19
M6 65.08 0.32 0.18 0.44 0.27
M7 49.63 0.24 0.13 0.34 0.19
M8 110.69 0.56 0.30 0.75 0.48
M9 89.81 0.46 0.24 0.61 0.40
M10 75.67 0.37 0.20 0.51 0.31
M11 48.88 0.24 0.13 0.33 0.20
M12 93.54 0.46 0.25 0.64 0.38
M13 52.92 0.26 0.25 0.36 0.21
M14 144.32 0.51 0.39 1.15 0.22
Average 76.29 0.36 0.21 0.53 0.28
Table 3. Comparison of radionuclides concentrations (Bq·kg1) and Raeq (Bq·kg1) in Marble Samples with those obtained in other
published data.
Country/region Material 226Ra (Bq·kg1) 232Th (Bq·kg1)40K (Bq·kg1)Ra
eq (Bq·kg1)Ref.
Egypt Marble tiles 56.78 ± 2.5 5.95 ± 1.2 142.8 ± 1.7 76.29 Presen work
Algerian Marble chips 23 ± 2 18 ± 2 310 ± 3 73 ± 4.1 Amrani and Tahtat(2001) [19]
Cameroonian Marbles
(by-products) 8 ± 2 0.35 ± 0.02 19 ± 2 10.15 M.Ngachin et al. (2007) [20]
Jordan( Azraq) Marbles
(by-products) 20.1 11.4 85 42.9
Ahmed and Hussein (1997)
Kuwait Marbles
(by-products) 3.9 ± 0.5 0.22 ± 0.08 3.7 ± 0.5 4.2 Bou-Rabee and Bem (1996)
Egypt (Qena) Marbles
(by-products) 205 ± 83 115 ± 60 865 ± 392 - Ahmed (2005) [23]
Saudi Arabia Marbles
(by-products 12.0 0.2 1.7 0.1 23.1 0.1 16.21 Fardous et al. (2007) [24]
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
Elemental Analysis’s of Material
Chemical composition of samples shows in Table 4
which forgets by using analysis (EDEX). The samples
marble M arrangement by increase the (Ca) element.
Major element composition of the marble M are quite
similar, but calc alkaline rocks are slightly richer in Fe,
Mg and Ca. Potassium feldspar is commonly microcline
and plagioclases are mainly sodic (i.e. albite and oligo-
clase). Quartz contents are similar, mica abundance is
variable, and biotite dominates over muscovite. The lat-
ter can be considered as an accessory mineral in some of
the analyzed rocks. The ESEM is used to investigate the
semi-quantitative of the elemental composition for this
region. It can be observed that in all of them, Ca is the
predominant, followed by Na, Mg. The M (10, 12, 13 14)
are characterized by appear Ti and M (12, 13, 14) appear
K meanwhile disappear in other samples. In sample M
(14) presents a significant amount of iron. The ESEM
analysis was made for the selected spot in sample No (14)
and the obtained results are shown in Table 4.
The chemical composition of the Marble samples are
summarized in Table 4. As the U and Th elemental con-
centrations (mg/kg) are below the detection limit of the
system used, the activity concentrations of 226Ra and
232Th (Bq·kg1) are measured using gamma spectrome-
try. Then, elemental concentrations of U, Th and K were
calculated using 226Ra, 232Th and 40K (Bq·kg1) activity
concentrations, respectively [25] Calculated values are
presented in Table 4 in units of ppm. Since Th and U
elements are considered because of radioactive toxicity,
it is important to check if they are above the interna-
tional levels or not. Permissible concentrations of Th and
U in the building materials should not exceed the inter-
nationally accepted levels of 20 and 10 mg/kg, respect-
tively [26]. The mean obtained values for Th and U are
within the international accepted values in general.
Table 4. Chemical composition of marble samples.
Al Si S Cl Ca Ti Fe Cu Commercial name, Element Region
0.13 - 0.06 0.03 97.83 - - 0.89 Glalla ElSuez M1 Suez Golf
0.04 0.07 0.06 0.01 94.61 - 0.04 0.33 Alpastar Odysyi M2 Sinai
0.37 0.46 0.15 0.03 93.76 - 0.35 0.0 5 AswadPrown M3 Sinai
0.15 0.09 0.12 0.08 93.49 - 0.00 0.40 Glalla KasKremy M4 Suez Golf
0.16 0.21 0.05 0.04 93.24 - 0.18 1.18 Red Glalla M5 Suez Golf
0.19 0.47 0.06 0.07 92.74 - 0.49 0.29 Prechaa M6 Sinai
0.58 2.01 0.08 0.10 91.95 - 0.49 0.29 Khatemaa M7 Sinai
0.65 1.23 0.16 0.18 91.33 - 0.72 0.28 Kerstin M8 Sinai
0.72 6.68 0.06 0.10 76.78 - 0.86 0.50 Rass Garp M9 Red Sea
0.18 1.01 0.23 0.05 67.95 0.62 0.36 0.67 Empradoor M10 Sinai
1.02 2.03 0.06 0.29 63.72 - 0.83 - Karara M11 Sinai
5.51 21.94 3.47 2.06 52.60 0.51 7.2 0.09 Kerstin South M112 Sinai
- 34.93 0.07 0.10 - 1.37 - 8.44 Zandpyaa M13 Aswan
13.18 26.42 0.09 0.25 3.76 12.411.59 14.35 Green Qena M14 Qena
K* Th* U* Zn K Na Mg Commercial name, Element Region
0.15 1.47 3.20 0.92 - - 0.15 Glalla ElSuez M1 Suez Golf
0.20 1.36 3.14 0.19 - 3.63 1.03 Alpastar Odysyi M2 Sinai
1.11 2.19 3.46 0.05 - 3.44 1.36 AswadPrown M3 Sinai
0.15 1.29 8.08 0.39 - 4.44 0.83 Glalla KasKremy M4 Suez Golf
0.13 1.08 3.02 0.87 - 3.40 0.67 Red Glalla M5 Suez Golf
0.13 1.38 4.38 0.27 - 3.50 0.93 Prechaa M6 Sinai
0.17 1.47 3.03 0.27 - 3.12 1.11 Khatemaa M7 Sinai
0.22 1.70 7.75 - - 4.31 1.18 Kerstin M8 Sinai
0.13 1.24 6.43 0.65 - 3.62 10.34 Rass Garp M9 Red Sea
0.12 1.86 5.02 0.80 - 6.58 21.55 Empradoor M10 Sinai
0.16 0.97 3.23 - - 2.22 29.83 Karara M11 Sinai
0.18 2.31 6.14 - 1.14 1.46 4.01 Kerstin South M112 Sinai
0.26 0.88 3.43 1.02 0.93 8.65 44.49 Zandpyaa M13 Aswan
4.62 1.38 3.56 1.90 1.80 2.63 21.61 Green Qena M14 Qena
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
X-ray diffraction technique has been used to investi-
gate the structure and characteristics of the prepared
samples. The obtained X-ray diffraction patterns of the
investigated powder samples are shown in Figure 3. The
XRD analysis showed three main peaks characteristic of
calcium minerals, while other minor phases are attrib-
uted to metallic impurities .This figure reveals that for
Table 3, there is diffraction peaks; the samples are found
in the crystalline states. On the contrary, the spectra of
X-ray diffraction pattern of samples M (1-14) exhibits
sharp diffraction lines (2θ 27 to 30) which belong to
crystalline (Ca). This means that this sample is crystal-
X-ray diffraction (XRD) analyses of (14) samples taken
from Egypt where the solid material proportion was
considerably high revealed that calcite mineral was the
main component for mixed, grey, yellow, green, black
and white colored samples [27].
Figure 3. XRD of Marble Samples.
The morphology of the pure sample is shown in Fig-
ure 4. Exhibit a continuous grain growth; meanwhile,
the crystalline phase does not propagate homogeneously
as it contains a mixture of amorphous and crystalline
regions. The changes continue, with change material,
resulting in amorphous-crystal phase change. The image
of the (1-14) marble powder or synthetic calcium car-
bonate (CaCO3) powder materials shows individual
grains, which are irregular in size & shape, and sepa-
rated by well defined inter—grain boundaries. The
droplets are substantially spherical and have convex
surfaces for samples M (1-8). Similar images have been
observed for other sample M (9-14), where the image
reflects the shape of island structures. As the calcium
carbonate increases, still amorphous except for few
grains that became crystallized owing to their polariza-
tion or orientation under the irradiation process.
Figure 4. SEM of marble samples.
S. Fares et al. / Natural Science 3 (2011) 895-905
Copyright © 2011 SciRes. OPEN ACCESS
The activity concentrations in studied Marble tiles of
wide use locally in Egypt in the building industry were
determined, employing high-resolution gamma-ray spec-
troscopy. The activity concentrations of 226Ra, 232Th and
40K in the Marble samples have been found to ranged
from (3.57 ± 0.64) to (9.37 ± 1.8) Bq·kg1 for 232Th,
(37.6 ± 1.7) to (100.54 ± 3.2) Bq kg1 for 226Ra and
(30.68 ± 81.1) to (1196 ± 4.9) Bq·kg1 for 40K. Accord-
ing to recommendation no. 112 issued by the European
Commission, any actual decision on restricting the use
of a material should be based on a separate dose assess-
ment. Such an assessment should be based on scenarios
where the material is used in a typical way for the type
of material in question. As it can be seen from Table 2,
the mean radioactive concentrations of 226Ra, 232Th and
40K of the Marble samples of this study are generally
safe, just like that of all other Marble sample referred to
in the literature. The natural radioactivity levels for the
Marble tiles measured in this study are comparable to
those measured on a worldwide scale. Apart from the
previously cited three Marbles, it is concluded: that all of
the studied materials are safe to use for dwelling con-
struction. It should be emphasized that accurate informa-
tion concerning the commercial names and origins of
these Marbles is very important because simple mistakes
with respect to that can produce serious economical and
social consequences in the stone market sector.
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