ABSTRACT
Characterization and analysis of Gwandu clay deposits has been conducted with a
view to finding its possible industrial applications. The chemical analysis was carried
out using XRF and thermal stability was determined using TGA. While the physical
property tests such as firing shrinkage, porosity, cold crushing strength, bulk density,
thermal shock resistance and refractoriness were done. The results of chemical
analysis indicates that Dabagi clay is composed of SiO2 (64.50%), Al2O3 (16.30%),
Fe2O3 (14.29%), CaO (0.29%), TiO2 (1.17%), K2O (0.74%), and other oxides in traces
and Fadama clay has SiO2 (55.90%), Al2O3 (13.90%), Fe2O3 (24.45%), CaO (0.75%),
TiO2 (1.71%), K2O (1.13%) and other oxides in traces. Termite hills clay on the other
hand gave SiO2 (25.00%), Al2O3 (6.30%), Fe2O3 (30.63%) CaO (1.00%), TiO2 (3.02%)
and other traces. However, the TG analysis shows the changes in the clays when
heated. The clays started losing water when heated up to 200 – 3000C.The significant
changes where observed between 5000C to 7000C where dehydration of clay material
occurred for Dabagi and Fadama clays. The results of the physical tests conducted
show: Dabagi has a Pa-38.46%, Bd-1.81g/cm3, LS- 6.80%, TSR-7 cycles, CCS-
5.44Km2, PCE-13 and LOI-4.46%. Fadama clay: Pa-40.29%, Bd-1.79g/cm3, LS-6.00%,
TSR-5 cycles, CCS-5.17Km2, PCE-13 and LOI-3.69%. And Termite clay: Pa- 46.15,
Bd-1.54g/cm3, LS-5.80%, TSR-3 cycles, CCS- 4.59Km2, PCE-12 and LOI-3.69.Rice
husk ash, kaolin and limestone clays were also incorporated (as an inert or non-plastic
additive) in the moulding mass which gave an improvement in the physical properties.
The results obtained confirmed that the clays are basically earthenware clays and can
be used in the bricks, tile, roof tile, drain tile and other heavy clay products production.
TABLE OF CONTENTS
CONTENT Page
Title page
Dedication ii
Certification iii
Acknowledgements iv
Table of contents v
List of tables ix
List of figures x
List of Abbreviations xi
Abstract xii
CHAPTER ONE: INTRODUCTION AND LITERITURE REVIEW
1.1 Research Background 1
1.2 Clay as Minerals 1
1.3 Clay Mineral Groups 2
1.4 Clay transformation on Heating 4
1.5 Characteristics of Clay Mineral 5
1.6 Categories of Ceramics 8
1.7 Clay types used in Ceramic Iindustries 10
vi
1.8 Rice husk ash 13
1.9 Limestone 14
1.10 Kaolin Clay 14
1.11 Principle of XRF 15
1.12 Theoretical Background of the Physical tests 15
1.13 Aim and Objectives 18
1.14 Justification of the study 18
1.15 Literature Review 19
1.15.1 Ceramics Raw Materials in Nigeria 19
CHAPTER TWO: MATERIALS AND METHODS
2.1 Materials and Equipments 42
2.2 Sampling Procedure 42
2.3 Samples Preparations 42
2.4 Determination of the chemical composition and
thermal Stability of clays 43
2.5 Loss on ignition (L O I) 44
2.6 Preparation of Clay Samples 45
2.7 Production of Rice Husk Ash 45
2.8 Preparation of Limestone Clay Sample 45
2.9 Preparation of Kaolin Clay Sample 46
2.10 Testing Procedures 46
2.10.1 Determination of Apparent Porosity and Bulk Density 46
2.10.2 Determination of Thermal Shock Resistance 47
vii
2.10.3 Determination of Linear Shrinkage 48
2.10.4 Determination of Refractoriness (PCE) 48
2.10.5 Determination of Cold Crushing Strength 49
2.11 Incorporation of Rice Husk Ash 50
2.12 Incorporation of Limestone 50
2.13 Incorporation of Kaolin Clay 51
CHAPTER THREE: RESULTS AND DISCUSION
3.1 Experimental Results 52
3.1.1 Results of Chemical composition and
thermal analysis of the clays 52
3.1 Thermogravimetric analysis of Dabagi Clay 53
3.2 Thermogravimetric analysis of Fadama Clay 54
3.3 Thermogravimetric analysis of Termite Hill Clay 55
3.1.2 Results of the physical properties of the clays 56
3.1.3 Physical properties of Dabagi clay with different
percentage of Rice Husk Ash 56
3.1.4 Results of the physical properties of Dabagi clay with different
percentage of Limestone 57
3.1.5 Results of the Physical Properties of Dabagi clay with different
viii
percentage of kaolin clay 58
3.1.6 Summary and comparison of the Properties 59
3.3 Discussion 60
CHAPTER FOUR CONCLUSIONS AND RECOMMENDATIONS
4.1 Conclusions 67
4.2 Recommendation 68
REFERENCE 69
APPENDECES 73
CHAPTER ONE
Introduction and literature review
1.0 Introduction
1.1 Research Background
A ceramic is an earthy material usually of silicate nature and may be defined as a
combination of one or more metals with a non-metallic element usually oxygen. The
American ceramic society (1986) had defined ceramics as inorganic non-metallic
materials, which are typically crystalline in nature, and are compounds formed between
metallic and non-metallic elements. Common examples are; silica – (SiO2) the main
ingredient in most glass products; alumina- (Al2O3), used in various applications from
abrasives to artificial bones; and more complex compounds such as hydrous aluminium
silicate (Al2Si2O5 (OH)4), the main ingredient in most clay product ( Reed, 2001). The
evaluation of the potential use of clay deposits in Gwandu town of Kebbi state in ceramic
production is the focus of the present study.
1.2 Clay as Minerals
Clays have been known and used by man since ages for varied purposes (Prentice, 1990).
clay has come to be defined as a natural earthy, fine-granular material that has a maximum
size of about two microns (2μ=0.002mm) that acquires plasticity on being mixed with
limited quantity of water (hydro-plasticity) and showing sheet-like crystallographic habit
(Velde, 1992; Ideniyi, 2003). From a chemical or mineralogical standpoint, clay is complex
2
aluminosilicate compounds containing attached water molecules, which have their origin in
the chemical and mechanical disintegration of rocks, such as granites (Nwajagu, 2005).
The term ‘mineral’ has several connotations. Used and strictly defined by the mineralogist,
it refers to a naturally occurring solid inorganic substance with distinctive physical
properties and a composition that can be described by a chemical formula (Mc Kelvery,
1986). Similarly, Hurbut and Klein (1977) observed that minerals are inorganic
homogenous crystalline solids with chemical composition and an ordered atomic
structure/arrangement.
1.3 Clay Mineral Groups
One basic property of clay minerals is the capacity of certain clays to change volume by
absorbing water molecules or other polar ions into their structure. This is called the swelling
property. Based on this property, Valde (1992) broadly classified all clays into swelling and
non-swelling type. Swelling clays are called smectites. The important property according to
Valde (1992) is the basic composition and structure of the clays; and this is used to further
classify the clay minerals into:
The Kaolinite group (Al2Si2O10 (OH6)): this group has one silica and one alumina unit
stacked in alternating fashion (1:1 lattice type). No ion or water molecules can enter the
adjacent layers, and only the external surfaces determine their colloidal properties. Owing
to its relatively large particles and low specific surface, kaolinite exhibits less plasticity,
cohesion and swelling as compared to other clay minerals.
3
The illite group KAl2 (Si3,Al)O10(OH)2: this group belongs to the hydrated micas within the
2:1 lattice type and consists of two silica and one single alumina unit. Aluminium (Al)
replaces the silicon (Si) in the silica units and the negative charges are compensated by
potassium (K) atoms which are partially embedded within the units and bind them firmly
together, so the expansion of the lattice is effectively prevented.
The vermiculite group: MgAl2 (Si3, Al)O10 (OH)2 this is similar to the illite group except
that the magnesium (Mg) rather than K is the exchangeable cation of the interlayer. As the
Mg ions are highly hydrated, both an interlayer of exchangeable cations and water hold the
units of the 2:1 lattice together.
The montmorillonite or smectite group (Mg, Ca) OAl2O3.5SiO2.H2O: is a 2:1 lattice clay
type and contains minerals like montmorillonite, beidellite and nontronite. Some substitution
of Al for Si has occurred in the silica unit and of Fe and Mg for Al in the alumina unit. The
layers are not tightly bound, so that water, ions and even organic compounds can enter
between them. This causes interlayer swelling and expansion of the crystal lattice, contrary
to the hydrated micas.
The chlorite group (Mg,Fe)4 Al4Si2O4(OH)8: has a 2:2 lattice type wherein Mg rather than
Al is the predominant ion in the alumina unit. Essentially, the chlorite structure consists of
two silica, one alumina and one magnesia unit. Substitution of Al for Si in the silica unit and
of Al and Fe for Mg in the magnesia unit results in electrostatic binding of the structural units.
(Raymond, 1990)
The attapulgite or palygorskite group: has a 2:1 lattice that extent in only one direction,
thus resulting in needle or chain-like minerals. Two silica units enclose the magnesia unit
4
because Mg predominates over Al. Isomorphous substitution of Al for Si in the silica unit is
rather small but isomorphous substitution of Al and some other cations such as iron (Fe) and
manganese (Mn) in the magnesia unit is high. (Borode, 2000)
1.4 Clay transformation on Heating
According to Velde (1992) there are four ranges of temperature which produces
characteristic transformations in clay materials. The free-water dehydration range (dryingrange)
(50-120oC); the clay stability range (120-600oC); the anhydrous clay range (600-
900oC); and the re-crystallization range (above 900oC)”. In the manufacture of ceramics
(bricks and tile inclusive), the 600-1000oC zone is of greatest importance in transforming the
dried clay into a new, more rigid substance. In this range the interaction of the clay and nonclay
additives occurs to form new materials or physical states (glass or new crystalline
phases).
In clays an important volume change (Shrinkage) takes place as they recrystallize into other
phases, losing their crystalline water above 1000oC (Velde, 1992). This loss is important to
the ceramic process. When firing brings the material into this thermal region, the shrinkage
effect must be modified by the addition of sufficient non-clay materials, called temper or grits,
sands of various types, pure quartz, alkali feldspar, grog (ground-up burned refractory
materials) chamotte (calcined and ground-up kaolinite or fire clay) are used depending on
the quality and use of the ceramic product (Nwajagu, 2005)
5
1.5 Characteristics of Clay Minerals
Plasticity
This is the most important characteristic of clays. The word clay comes from the
German verb kleben, “to sticks” to and that is of course, what immediately comes to
mind when we think of clay. It is a material that “sticks to” the hand and “sticks to” itself
in respond to the touch of the hand. In other words, the identifying characteristic of
plasticity is intrinsic to the meaning of the word clay.
Plasticity refers to the ability of materials to form and retain the shape directed by an
outside force. “This is one of the most important of the properties of clay and one
which is least understood”. The plasticity of most clay minerals derives from the unique
crystal structure of their molecules, which are minute in size and platelike in shape.
These crystals form flat, two dimensional sheets that touch each other on only two
sides. There is a disproportionately large ratio of surface area to mass in these platy
crystals. When water floods these two-dimensional sheets, it creates a strong bond
between them in much the same way that a wet, flat plate bonds to a table surface.
The water also acts as a lubricant and causes the platy crystals to slide over one
another. The strongly bonded, sliding sheets will take on whatever shape they are
directed toward by an outside force.
Particle Sizes
6
Particle size is an all-important characteristic of clay minerals and is of crucial
importance in the identification of clay minerals. All clay minerals possess a fine
grained, minute particle size. “Clays are characterized primarily by their small particle
size, which is usually taken as less than 2μm. Coarse, medium and fine clays have
ranges about 2.0-0.5, 0.5-0.2, and below 0.2μm respectively.
Subject to the exception noted above, the fineness of the particle size determines the
plasticity of the clay mineral. The minute clay crystal contains more surface area and
therefore greater water-bonding capacity than the larger particle size crystals of other
materials, such as feldspar. Consequently, the bonds between the clay particles and
the sliding power produced by water increase in strength as the particles become
smaller and minute. Hence, clay with smaller particle sizes is more plastic and takes
on more water than clays with a larger particle size.
Chemical and Crystalline Structure
All clays contain significant amount of silica (SiO2), alumina (Al2O3) and water (H2O).
More important is the fact that the atoms are bonded together in flat, two-dimensional
sheets of two or more layers. Sheets of silica, alumina, and other metallic oxides are
interspersed with sheets of hydrogen-oxygen molecules (HOH). The top layer consists
of silicon and oxygen atoms; the second layer is alumina and (in the case of clay
minerals other than perfectly ordered kaolinite) other metallic ions such as magnesium,
calcium, iron, sodium, and potassium. The third layer contains the hydrogen and
oxygen atoms. It is the second layer of aluminium and other metallic atoms that holds
the most interest. This is the layer in which exchanges of aluminium are made with
7
other metallic atoms. The exchange property of the aluminum layers create the
complexity and disorder of some clay molecules, for here, many different atoms can
appear. This fascinating exchange property includes the ability to store, exchange, and
transfer energy, and it is the reason certain clays are thought to be a possible link
between inorganic and organic matter. (Callister, 2003)
Metamorphosis by Fire
A unique feature of clay is their metamorphosis by fire into a stronger material. Most
earth materials are weakened and broken by the heat of the fire. Clays, on the other
hand, exchange their fragile and perishable existence for a hard, durable form that is
capable of lasting for thousands of years. They become hard, water- impermeable
materials with a new crystalline structure and different physical properties. (Ijagbemi,
2005)
Shrinkage
Shrinkage is the loss in volume of clay when it dries or when it is fired. Both drying
and firing shrinkages are important properties of clay used for structured clay products.
Drying shrinkage is dependent on water content, the character of the clay minerals, and
the particle size of the constituents. Drying shrinkages is high in almost every plastic clay
and tends to produce a week, porous body. Montmorillonite in relatively large amounts
(10-25%) cause excessive shrinkage, cracking, and slow drying. Firing shrinkage on the
other hand depends on the volatile materials preset, the types of crystalline phase
changes that take place during firing, and the dehydration characteristic of the clay
minerals (Parker, 1982).
8
Colour
Colour is important in most structural clay products, particularly the maintenance of
uniform colour. The colour of a product is influenced by firing temperature and degree
of vitrification, the proportion of alumina, lime, and magnesia in the clay material, and
the composition of the fire gases during the burning operation. The best white-burning
clays contain less than 1% Fe2O3. Buff burning clays contain 1-5% Fe2O3 and redburning
clays contain 5% of more Fe2O3 (Parker, 1982).
1.6 Categories of Ceramics
Ceramics are classified into three basic categories; these are:
Traditional Ceramics:
These are ceramics based on mineral silicate, silica, and mineral oxides that are found
in nature. The primary products are fired clay (pottery, tableware, brick and tile),
cement, and natural abrasives such as alumina. The mineral silicates, such as clays of
various compositions, and silica, such as quartz, are among the most abundant
substances in nature and constitute the principal raw-materials for traditional ceramics.
(Basoum, 1997).
New Ceramics
The term new ceramics refers to improvements in processing techniques that provide
greater control over the structures and properties of ceramic materials. In general, new
ceramics are based on compounds other than variations of aluminum silicate, which
9
form most of the traditional ceramic materials. New ceramics are ceramic materials
developed synthetically over the last several decades, usually simpler chemically than
traditional ceramics for example oxides, carbides, nitrides, and borides. (Barsoum,
1997)
Glass
As a type of ceramic, glass is an inorganic, non-metallic compound (or mixture of
compounds) that cools to a rigid condition without crystallizing, or is essentially an
amorphous solid made by fusing silica (silicon dioxide) with basic oxides which has been
cooled to a hard condition without crystallization (Burgmn, 1970). Glasses are based
primarily on silica and distinguished by their non-crystalline structure. Other ingredients in
glass include: Sodium oxide (Na2O), calcium oxide (CaO), aluminum oxide (Al2O3),
Magnesium oxide (MgO), Potassium oxide (K2O), Lead oxide (PbO), and Boron Oxide
(B2O3). The importances of these ingredients are: They act as flux (promoting fusion)
during heating, increase fluidity in molten glass for processing; improve chemical
resistance against attack by acids, basic substances, or water, add color to the glass.
The actual silica sand requirements in glass making process fall into two groups
namely: the degree of purity, indicated by the chemical composition of the sand and
the natural physical state of the sand. (Waudby, 1994). Irrespective of glass to be
manufacture, the degree of purity required varies. According to Tooley (1987) iron
content is perhaps the most critical chemical component for all glass making raw
materials. Iron control is important because of its effect on glass colour particularly
white and flint glasses (Reed, 2001)
10
1.7 Clay types used in Ceramic Industries
Kaolin or China Clay
Though relatively scarce in nature, kaolin is of particular interest to potter. It is
indispensable in the making of pure white porcelain or china clay. The whitest-burning
kaolin clays, and hence the most pure, are primary clay that were weathered at the site
of the feldspar. They are coarse in particle size and are therefore less plastic
compared to most sedimentary clays. In chemical composition kaolins approach the
formula of the mineral kaolinite (Al2O3.2SiO2.2H2O). Kaolin is highly refractory clay and
has a melting point above 18000C. Used by itself, kaolin is difficult to shape into
objects because of its poor plasticity, and also, because of its refractoriness, it is
difficult to mature by firing to a hard, dense object. In practice, therefore, kaolin is
seldom used by itself; other materials are added to it to increase it workability and to
lower the kiln temperature necessary to produce a hard; dense product. As would be
expected, the shrinkage of the kaolin is low because of its relatively coarse grain
structure, and it has a little dry strength (Omowumi, 2000)
Ball clay
Ball clay are somewhat the opposite; of kaolin in their properties. They are high in iron
content, more fusible, much more plastic, and fine in particle size. Ball clay and kaolin
clay are really complementary in character and are often combine in clay bodies to
adjust the mixture toward practical, workable clay.
Ball clay is highly plastic, although not so pure as kaolin; it is relatively free from iron
and other mineral impurities and burns to a light gray or light buff colour. It tightens into
11
a dense structure when fired to about 18000C. Different ball clays vary considerably in
composition.
Ball clays are impossible to be use alone in pottery because of their excessive
shrinkage, which may be as high as 20 percent when fired to maturity. They are
usually used as an admixture to other clays to gain increase plasticity and workability.
In manufacturing whitewares, ball clay is indispensable as an addition to the body to
overcome the nonplastic properties of kaolin. However, if whitness is desired, not more
than about 15 percent of ball clay can be added to a clay body; more than this amount
in a whiteware body results in a gray, off-white, or buff colour. The presence of ball
clay in a porcelain body decreases its translucence.
Fire clay
Fire clay is not so well defined as a type of clay as either ball clay or kaolin. The term
‘fire clay’ refers to refractoriness or resistance to heat and clays which vary widely in
other properties may be called fire clays if they are refractory. Some fire clays are very
plastic and some lack plasticity, and the fired colour may vary. Any clay which resists
fusion or deformation up to about 15000C may be called fire clay. Such refractoriness
or resistance to heat means that the clay is relatively pure and free from iron, although
most fire clays burn to a buff or brownish colour. Sometimes with darker splotches due
to the concentrations of iron-bearing minerals. (John, 2003)
Fire clays are useful for a great variety of products, principally in the manufacture of
fire brick and other refractory parts of kilns, furnaces, boilers, and melting pots.
12
Industries such as steel, copper, and other metallurgical industries could not operate
without fire brick furnaces in which high-temperature smelting is done.
Stoneware Clay
Stoneware clays are plastic clays which mature or become vitreous at 12000C to
13000C. Their fired colour ranges from a light gray or buff to a darker gray or brown.
Stoneware clays are secondary or sedimentary clays. They vary widely in colour,
plasticity, and firing range, and there is no sharp distinction between what might be
called a fire clay or stoneware clay. The classification really hinges upon the possible
use of the clay in ceramics, rather than upon the actual chemical or physical nature of
the clay or its geological. One clay, for instance, might be successfully used both as a
fire in the making of bricks and refractories and as a stoneware clay in the making of
high-fired stoneware. Many types of clay are quite suitable for making stoneware
without any additions. Such clays may have just the right plasticity for wheel and may
have desirable drying and firing characteristics.
Earthenware Clay
Most of the usable clay found in nature might be called ‘earthenware’ clay or common
clay. These clays contain iron and other mineral impurities in sufficient quantity to
cause the clay to become tight and hard-fired at 9500C-11000C. In the raw such clay is
red, brown, greenish, or gray, as a result of the presence of iron oxide. Fired, the clay
may vary in colour from pink to buff to tan, red, brown, or black, depending on the clay
and the condition of the firing. Most of the pottery the world over has been made of
13
earthenware clay, and it is also the common raw material for brick, tile, drain tile, roof
tile, and the other heavy clay products (Adams, 1979).
1.8 Rice husk ash
Rice husk ash contains a high amount of organic volatiles. Thus, the rice husk ash is
recognized as a potential source of energy. Moreover its ≈ 20% ash content comprising
of over 95% amorphous silica would make the rice husk ash utilization economically
attractive. Rice husk is a milling by-product of the agriculture industry, it also abundantly
available. Rice is a residue produced in significant quantity on a global basis while they
are used as fuel in some regions, in other countries they are treated as waste, causing
pollution and disposal problems. Due to growing environmental concern and the need to
conserve energy and resources, efforts have been made to burn the husks under
controlled conditions and utilize the resultant ash as building material. (Raymond, 1990)
Rice husk contains a high amount of silicon dioxide. The non-crystalline phase in rice
husk ash obtained from combustion at temperature below 6000C consists primarily of a
disordered Si-O structure. It is the product of decomposition and sintering of hydrous
silica that result without melting. Occasionally, a small amount of crystalline impurities
may be present, including quartz, cristobalite. When by burning the rice husk under
controlled temperature and atmosphere, highly reactive rice husk ash can is obtained
(Adekale, 2001).
1.9 Limestone
14
Limestone comprises more than 4% of the earth’s crust as limestone, marble and
chalk, as well as in natural ores like calcite. It is found throughout the world. Limestone
is a white solid which is insoluble in pure distilled water. However, it is a source of
basic refractory oxide, i.e. calcium oxide (lime), very sensitive to hydration. As an
additives, e.g. in glass batches, enamels or pottery, used in the form of ‘whiting’, I.e.
calcium carbonate (limestone) with some impurity of magnesium carbonate (forming
together dolomite). Used in construction as marble (crystallized limestone) (Lawal,
2005)
1.10 Kaolin Clay
White-burning clays formed by weathering of feldspathic rocks, granites, etc.
secondary kaolins are formed by weathering then transported and redeposited
elsewhere (Aliyu, 1996). Kaolin is also called china clay or porcelain clay, and is the
refractory clay that characterizes fireclays (ILO/UNIDO, 1984; Idenyi and Nwajagu,
2003). The basic rocks from which clays are formed are complex aluminosilicates.
During weathering, these become hydrolyzed, the alkali and alkaline earth ions form
soluble salts and are leached out. The remainder consists of hydrated aluminosilicates
of varying compositions and structures, and free silica (Hurlburt and Klein, 1977). The
process can be represented by the following equations
K2O.Al2O3.6SiO2 + H2O → Al2O3.6SiO2.2H2O + 2K+ [Hydrolysis] (potassium feldspar)
Al2O3.6SiO2.2H2O → Al2O3.2SiO2.2H2O + 4SiO2 [Desilication]
(kaolinite)
1.11 Principle of XRF
15
X-ray is a type of electromagnetic waves such as visible light ray, but the key
difference is its extremely short wavelength, measuring from 100A to 0.1A. And
compared to normal electromagnetic waves, X-ray easily passes though material and it
becomes stronger as the material’s atomic number decreases. X-ray fluorescence
analysis is a method that uses the characteristic X- ray (fluorescent X-ray) that is
generated when X-ray is irradiated on a substance. The fluorescent is the excess
energy irradiated as electromagnetic field, which is generated when the irradiated Xray
forces the constituent atom’s inner-shell electrons to the outer shell and the vacant
space (acceptor) falls on the outer-shell electrons. These rays possess energy
characteristic to each element, and qualitative analysis using Mosley’s Equation and
quantitative analysis using the energy’s X- ray intensity (number of photons) are
possible.
X-ray fluorescence analysis can be considered as spetrochemical analysis of an X-ray
region. It has the same characteristics as atomic absorption spectrometry and optical
emission spectrometry which conduct measurement by putting the sample into
solution. For example, in flameless atomic absorption spectrometry (FLASS), elements
in the sample are atomized in 2000 to 3000C flame and in ICP atomic emission
spectrometry (ICP-AES), sample is exited 6000 to 9000C plasma flame. X-ray
fluorescence likewise excited the sample using X-ray to obtain information (Adams,
1979).
X-ray fluorescence instruments are either energy dispersive x-ray fluorescence
(EDXRF) or wavelength dispersive (WDXRF) spectrometers. WDXRF disperses the
fluorescent X-ray generated in the sample using dispersion crystal and measures it
16
goniometer, resulting in a large size. On the other hand, the detector in EDXRF has a
superior energy resolution and requires no dispersion system, which enables
downsizing of the device.
X-ray is generated when the X-ray tube accelerates the electrons at high voltage and
bombards them against the metal anode (anti-cathode). There are two types of X-ray
tubes, side window type and end window type, and both are designed to irradiate
intense X-ray on the sample surface as evenly as possible.
1.12 Theoretical Background of the Physical tests
When choosing a particular clay material for a particular application, a variety of
physical properties must be considered, e.g. bulk density, apparent porosity, linear
shrinkage, thermal shock resistance, refractoriness and strength at room temperature.
(Ruh, 1986). The density, strength and porosity of fired products are influenced by
factors like quality of the materials, the size and ‘fit’ of the particles, moisture content at
the time of moulding, pressure of moulding, temperature and duration of firing, kiln
atmosphere and cooling rate (Idenyi and Nwajagu, 2003).
Apparent Porosity
This is the ability of the clay materials to be impervious to gasses and liquids. Pores
are formed as water and gasses are given off during firing process (Adams, 1979).
Open pores are those pores that are open to the surface of the clay, i.e.
communicating with the atmosphere. Clay with low apparent porosity has greater
resistance to penetration by slags and fluxes, resistance to corrosion and erosion and
17
usually lower gas permeability than those with high porosity (Krivandin and Markov,
1980)
Bulk density
This is the mass per unit volume of the clay ignoring the volume occupied by pores.
Bulk density depends upon the true specific gravity and porosity (Adams, 1979).
Density of all clay materials is an indirect measure of their capacity to store heat- a
particularly useful property in heat exchanger (refrigerator) installation (Idenyi and
Nwajagu, 2003).
Cold crushing strength
This is the ability of the clay materials to bear load. This is an important indicator of the
clay to withstand handling or shipping at low temperature. It does not, however, give
an indication of the clay’s strength at a given temperature (Ruh, 1986).
Thermal shock (spalling) resistance
Thermal stability is the ability of the clay to withstand heating and cooling several times
before a deep crack appears. The number of thermal cycles (i.e. heating and sharp
quenching in water or air) a clay can undergo characterized spalling resistance
(Krivandin and Markov, 1980).
Linear shrinkage
This is a property of the clay which makes it to undergo least structural changes and
disintegration while being heated. The shape and size stability is very important, these
18
may deform (shrink, change shape or size) during processing stages of drying and
firing (Krivandin and Markov).
Refractoriness
This is the resistance of the clay to fusion and softening at high working temperatures.
It is the maximum temperature clay can withstand with no load applied (Krivandind and
Markov, 1980)
1.13 Aim and Objectives
The aim of this research is to determine the potential use of some clay deposits in ceramic
production in Gwandu town and the objectives are
1. To determine the actual chemical composition of the clays from three deposits in
Gwandu town;
2. To determine the thermal stability of the clays
3. To determine the physical properties of the clay samples
4. To assess the potential uses of the clay samples from the results of the chemical
analyses and characterization;
5. To determine the effect of additives (rice husk ash, limestone and kaolin clays. on the
physical properties of the clay sample
1.14 Justification
Ceramics are one of the important materials in human civilization. Their socioeconomic
impact is as important today as it has being throughout the history. The ceramic need of
19
Nigeria –a developing industrial nation is potentially enormous. The country expends a
lot of foreign exchange importing ceramic materials. Yet, a lot of clay deposits abound
in the country, which can be developed to meet our local needs. Earlier work on various
Nigerian clay deposits have being carried out. However, a number of deposits were
found suitable for use as ceramic materials; that is, if properly processed. Gwandu town
clay deposit, which has been the source of raw material for most potters in Gwandu, is
one of the unidentified clay deposits in Nigeria. However, no work has been done to
characterize its properties. Therefore it’s my hope that this study will provide at least
baseline information on the potential use of the clays in ceramic production.
1.15.0 Literature Review
1.15.1 Ceramics Raw Materials in Nigeria
The exploitation and processing of ceramic raw materials are enough to influence
development and capacity building among the local miners around the communities
where they are located. The minerals as stated below from Raw Material Research
and Development Council (2003) and Raw Material Research and Development
Council (2008), indicates the originating states and locations of Feldspar, kaolin,
Quartz, limestone, silica sand, Talc, ball clay, and bentonite (RMRDC, 2003).
Phosphate
Phosphate rock refers to a mineral assemblage that occurs naturally with an
exceptionally high concentration of phosphate minerals. Phosphate usually occurs as
the mineral apatite, CaF(PO4)3 in igneous rocks. It may be derived from a number of
sources but the most common is the one that contains high concentration of
phosphates in nodular or compact masses.
20
Phosphate fertilizer and detergents are the major user industries of phosphate rock.
Metal treatment, water treatment, pulp and paper, glass and ceramics, textiles,
plastics, rubber, pharmaceuticals and cosmetics, petroleum production, toothpaste,
paints, fuels, cells are other end- users industries of phosphate rock.
Locations of Phosphate Deposits in Nigeria
The Nigerian phosphate rock deposits are sedimentary in origin. They occur mostly in
granular, nodular and vesicular forms with an average weight percentage of P2O5
varying from 34.5 to 36.25% (RMRDC, 2006).
Occurrences of phosphate rock are known in Sokoto, Abia, Cross River, Kogi, Ondo
and Ogun States. The deposits of phosphate beds in Sokoto embayment represent
southward extension of the deposits in Niger Republic. The deposits are found within
the geological features termed the illummenden Basin.
The occurrence of phosphate in Sokoto State was first reported in 1948 by B. Jones of
the Geological surveys. It occurs in the Sokoto group of sediments which consist of the
Dange, Kalambaina Formations. The Dange formation consists of slightly indurated
bluish grey shale with a thickness of about 22m. The shale includes bands of fibrous
gypsum with a large number of irregular shaped phosphate nodules. The nodules are
characteristically marked with irregular striations. The nodules have a dirty white
colour externally but bluish grey internally. The Kalambaina formation consists of
clayey limestone and shale, invariably with phosphate. The specific areas of
concentration of phosphate nodules in Sokoto basin include: Dange, Gidan Bauchi,
Illela, Gada, Wurno, Gwadabawa etc. Pitting and experimental mining in Sokoto basin
carried out by Nigerian Mining Corporation (NMC) in Zorow, Shagari and Gwadabawa
21
over an area of 4km 2 yields average weight % P2O5 of 34.50 – 36.25%. Table 1.4.2 of
phosphate occurrence in Nigeria is given below:
Table 1.4.1 Chemical Analysis of Phosphate Rock in Nigeria
Wt % SOKOTO -1 SOKOTO -2 OGUN-2 OGUN-2
P2O5 36.25 34.20 31.38 31.99
CaO 52.30 47.90 31.68 38.43
SiO2 3.44 4.20 6.68 4.40
Al2O3 1.50 1.50 1.70 11.50
Fe2O3 1.50 1.50 3.00 4.58
B2O NA NA 0.24 NA
N2O NA NA 0.10 NA
K2O NA NA 0.08 NA
H2O 0.75 0.76 0.77 NA
NA: not available,Source: Raw Materials Research and Development Council (2010)
Table 1.4.2 Locations of Phosphate Deposits Nigeria
S/N STATE LOCATIONS ESTIMATE
D
RESERVE
REMARKS
1 Abia Bende, Umuahia,
Ikwuamo
Not yet
ascertain
Need further investigation.
2 Cross River Akpet, Ugep
Not
available
Further investigation.
3 Ogun Ifo, Ilaro Not yet
estimated
Further investigation
required. The RMRDC and
Ogun State Government are
jointly establishing a
processing plant at Ilaro
4 Sokoto Bodinga, Dange,
Shuni, Gada, Yabo,
Gwadabawa,
Goronyo, Shagari,
Raba, Wurno etc.
The RMRDC in collaboration
with the Sokoto State
Government and other
private investors have
phosphate beneficiation
plants.
5 Ondo Ifon
Further investigation
required.
6 Kogi Lokoja
Further investigation
required.
Source: Raw Materials Research and Development Council (2010).
Glass Sand/Quartz
22
Silica sand/Quartz constitutes one of the most readily available geological materials
used in industries and factories such as glass manufacturing companies. Silica
sand/Quartz are said to consist of high optimal percentage of silicon oxide (SiO2)
which is a very good chemically stable element and it remains almost the same no
matter the series of cycles it may have gone through, either in transportation or redeposition.
Quartz is silica occurring alone in pure state. Silica/glass sand on the other
hand are products of weathering, erosion and transportation by rivers or/ and the sea.
Naturally occurring silica sands may contain some undesirable impurities like
accessory haematite, rutile and dolomite etc.
The glass sand is used in the production of various glass products: which include
sheet glasses, for windows, bottles, mirrors, optical instruments, chemical apparatus,
electrical insulation and condensers, pipe, doors, crucibles, automobile and aircraft
bodies, filters and building blocks. They are also used for making abrasives and for
gravel parking in the petroleum industries.
Locations of Glass Sand/Quartz deposits in Nigeria
Commercially exploitable quartz rock crystal occur in pegmatites and quartzites hosted
by rock of thebasement complex around Egbe, Udiarehu, Okene and Lokoja in Kogi
state, Ijero in Ekiti state. The quartzites occur in the medium to high grade
metamorphic terrains of the basement complex. The vein quartz and quartz bearing
pegmatites solidified from the hydrothermal fluids associated with the older granites as
well as those of the younger granites and from the materials of the rocks of the
basement complex at different periods.
23
Nigeria has extensive deposits of good quartz silica sands. Many of which are
associated with the coastal plain of the sedimentary areas in the southern part of the
country, although deposits also occur in some inland areas. The major silica sand
deposits in the country are located at Ughecll- Delta State, Igbokoda, Ondo State,
Baure Katsina State, Badagry, Logas State, and along the sandy shore line of the
Atlantic, some inland deposits are also reported at Shebu, Plateau State and Ilaro,
Ogun State. Table 1.4.3 shows locations of some quartz deposits while 1.4.4 is that of
silica sand.
Table 1.4.3 Locations of Quartz Deposits in Nigeria
S/N STATE LOCATIONS ESTIMETED
RESERVE
REMARKS
1 Ebonyi Ohaozara, Abakaliki Not available More
investigation
work required
2 Ekiti Idao, Iroko, Aiyegunle, Efon,
Alaaye, Okemesi
23.817 million
metric tones
More
investigation
work required
3 Plateau Mangu, Pankshin, Kanassm,
Langtang
4 Niger Duku-Rijau, Gurara
5 Kogi Okene, Okehi, Egbe
6 Katsina Faskari, Bakori, Kurfi, Funtua Not available Not being
exploited
7 Kebbi Danko, Wasagu Not available
Source: Raw Materials Research and Development council (2008)
Table 1.4.4. Locations of Glass Sand Deposits in Nigeria
S/N STATE LOCATIONS REMARKS
24
1 Cross
River
Ikom, Ibine Oban, Mfamoshig, aoarotong,
etc.
Yet to be
investigated
2 Akwa –
ibom
Iwuo Ukem, Ibeno beach, Mbo, Oron
3 Benue Buruku, Gboko, Guma, Katsina-Alu,
Makurdi, Vandeikya, Agati, Logo
Quarrying activities
are in some
locations
4 Abia Ukwa, Aba, Isiala-Ngwa, Isiala Quarrying at Ukwa
5 Imo Ihiagwa, Obinze, Isu, Njeba, Obowo. More investigation
6 Enugu Enugu-Ekulu, Igbo Eze, Isi-Uzo, Nkanut,
Udi, etc.
Investigation by
PRODA
7 Lagos Apapa, Badagry, Epe, Ibeju-Lekki, Lagos
Island,
Being exploited
8 Ondo Igbokoda, Akata-Agbala, Abotoe, Ese-Odo Partial investigation
9 Niger Gbako, Gurara, Lavun, Mokwa, Muya,
Bida etc.
Preliminary
investigation
10 Nasarawa Lafia, Done, Nasarawa Partial investigation
11 Kaduna Kaduna Partial investigation
12 Gombe Yamaltu-Deba, Akko, Dukko.
13 Sokoto Sabon Birni, Silame, Wamako
14 Zamfara Jarmuna, Gummi
15 Katsina Zango, Baure Notbeing exploited
Source: Raw Materials Research and Development Council (2010)
Table 1.4.5 Chemical Analysis of Igbokoda Silica Sand/quartz
25
Composition (I) (II) (III) (IV)
SiO2 % 99.91 99.83 99.71 99.91
Al2O3 (PPM) 20 190 33 9.0
Fe2O3 393 754 1358 277
MnO 13 97 45 14
MgO 74 135 222 136
CaO 22 51 14 40
Na2O 278 241 169 199
K2O 213 307 48 102
Cr 0.8 0.7 6.9 1.9
CO 8.7 12 16 78
Depth of
sample (M)
Surface Surface Surface 2.3
Source: Raw Materials Research and Development Council (2010).
Limestone/marble
High quality marble/limestone suitable for the production of cement, fluxing material,
powder filler for paper , rubber, paint, glass, ceramics. Pharmaceutical, quicklime,
hydrated lime, calcium carbonate etc. exist greater abundance in the sedimentary
basins and crystalline basement belt.
Limestone/marble Deposits in Nigeria
Limestone is widespread in the sedimentary basins of Nigeria. It is used extensively in
cement production, as flux and refractory material, metallurgical applications etc.
26
prominent reserve has been proved to exist all over the country. The marble and
dolomite deposits in Nigeria are often associated with the meta-sediments such as
schist, amphibolites complex and metal-conglomerates. They are also used as flux in
steel making. The table 1.4.6, and 1.4.7, show the locations of the marble/dolomite and
limestone deposits in Nigeria respectively.
27
Table 1.4.6 Location of Marble/ Dolomite Deposits in Nigeria
S/N STATE LOCATION ESTIMETED
RESERVE
million tones
REMARKS
1 Ebonyi Afikpo North,
Abakaliki,
Ohaozara, Ezza
20 Quarrying mainly at Ezza
North and South.
2 Abia Ohafia Need for more
investigation
3 Imo Okigwe Further investigation
4 Nasarawa Toto-Muto Hills 10.6 Further investigation
5 Kogi Ekinrin-
AdoElebu,
Osara
Jakura
Ubo, Ajakuta
Not available
17
68.00
20.00
Further investigation
Dolomite/Marblecommercial
exploitation
6 Benue Itobe 10.00 Further investigation
7 Niger Kwakuti
Takalafia
2.5
4.0
Dolomite –commercial
exploitation
8 FCT Burum
Takusara
16.6
12.0
Dolomite –commercial
exploitation
9 Katsina Kankara,
Malunfashi
Not available Further investigation
Source: Raw Materials Research and Development Council (2010)
28
Table 1.4.7 Location of limestone Deposits in Nigeria.
S/N STATE LOCATIONS ESTIMETED
RESERVE
(million tones)
REMARKS
1 Cross River Mfamosing, Odukpani,Uwet,
Akpa, Okranibang, Ugep etc.
Commercially
quantities
2 Akwa-Ibom Obotime Need further
investigation
3 Imo Okigwe,Umu-obon 10 Need further
investigation
4 Abia Aba, Amachi, Arochukwu,
Ohafia, Bende
Need further
investigation
5 Anambara Njikoka Not available
6 Ebonyi Afikpo, Abakaliki, Ikwo, Ishielu About i5.5 Quarrying is
being carried out
7 Enugu Nkalagu,Nkanu, Awgu,
Aninri,Odomoke
Commercial
exploitation
8 Benue Gboko,Gwer, Yendev,
Konshisha,Oju, Markudi etc.
Possible over 40
million tones
Exploitation by
Benue cement
9 Ogun Ewekoro, Sagamu 185 Exploitation by
WAPCO
10 Sokoto Kalambaina 101.6 Exploitation by
CCNN
11 Nasarawa Awe
12 Gombe Ashaka, Pindiga, Gombe,
Deba, Funakaye, Nafada etc.
13 Yobe Garin Ari, Turm (Fika) deda,
Kwayaya (Fune)
14 Adamawa Guyuk, Shelleng, Nguroru,
Numan,
15 Kebbi Jega Not available Not available
Source: Raw Materials Research and Development Council (2010)
29
Ball Clay
This noted for its plastic nature- a property which is a direct result of the clay’s fine
grain sizes. It has appreciable amount of organic matter and expendable smeltic/mixed
layer clays. Ball clay is used in the manufacture of foundry crucible in furnace lining
where ball clay provides the plasticity required for easy shaping and also serve as a
bonding agent.
Ball Clay Deposits in Nigeria
Various grades of ball clay occur in Nigeria. Occurrences are in Niger Delta and
coastlines, Akabuka, Komo-Boue, Kwawa etc. in Rivers State. Iguiriaki, Aboh, and
Uzere in Edo State and, Eket and Etinam in Akwa Ibom State. Table 1.4.9 presents the
locations of some of the clay deposits, Table 1.4.10, presents the chemical
composition, while table 1.4.11, presents ball clay specifications for some products.
The ball clays are suitable for the production of bricks, fillers and ceramics wares
although the highly plastic varieties require the addition of cohesive sand.
30
Table 1.4.8 Locations of Ball Clays in Nigeria
S/N STATE LOCATIONS REMARKS
1 Cross
River
Appiapume,Ofumbonghaone Ogurude,
Ovonum
Detailed
investigation
required
2 Akwa-Ibom Nkari, Nlung, Ukim, Ekot-Etim, Eket-Uyo,
Ekpere-Obom Ikot-Okoro, Ikwa
Detailed
investigation
required
3 Benue Katsina-Ala, Otukpo,Bukuru, Gwer, Makurdi
4 Ebonyi Ohaukwu, Ezza North, Abakaliki,Ezzi,
Afikpo south, Ohaozara
Quarried locally for
pottery
5 Abia Isikwuato, Ikwuano, Umuahia, Bende,
Arochukwu
More investigation
required
6 Enugu Enugu, Isi-Uzo, Uzo- Uwani, Oji River, Udi Used for pottery
7 Ekiti Ara-Ijero, Igbara, Ado EKiti Detail investigation
required
8 Plateau Bassa, Barikin-Ladi, Mangu, Kanam,
Langtang North
9 Niger Lavu, Gboko Suleja, Minna Agaje, Paiko Being exploited
10 Kaduna Kachia, Maraba-Rido, Farin- Kassa
11 Kano All over
Source: Raw Materials Research and Development Council (2009)
31
Table 1.4.9 Specifications for Ball Clay
Descriptions Table wares Sanitary wares Tiles
SiO2 46.0 54.0 70.0
Al2O3 31.0 30.0 19.0
Fe2O3 1.1 1.4 1.6
TiO2 0.9 1.2 1.6
MgO 0.4 0.4 0.4
CaO 0.4 0.3 0.2
K2O 2.2 3.1 2.0
Na2O 0.4 0.5 0.5
L.O.I 17.5 8.8 5.4
Fired brightness
(11200C)
75.0 63.0 63.0
PCE 35.0 32.0 28.0
Source: Raw Materials Research and Development Council (2010)
Kaolin
Kaolin is an important and widely used industrial mineral which is refined from
kaolinite. It is a naturally occurring minerals of the clay family and may contain a
number of impurities such as quartz, feldspar, tourmaline, limestone, zircon, etc. which
were derived from the parent rock. It is a weathering product of silicate rocks which is
whitish, earthy to dull with plastic touch. The characteristics and chemical composition
of a kaolin deposit usually determines its industrial utilization. (RMRDC, 2010)
Kaolin is one of the most valuable of the industrial clays which is used in most
manufactured products. Prominent uses include paper filling and coating; paint, plastic,
32
adhesive and ink pigment; rubber reinforcing agent, ceramic raw materials for
porcelain, dinner ware, tiles and enamels, catalyst for petroleum cracking and auto
exhaust emission catalytic control devices; cosmetics base; and digestive coating
remedy.
Kaolin has numerous industrial applications and new ones are still being discovered. It
is a unique industrial mineral because it is chemically inert over a relative wide pH
range. It is suitable for moulding mixture in cast iron and steel foundry, and insulator
refractories where the most important properties are plasticity, strength and fired
colour.
Kaolin Deposits in Nigeria
The bulk of the kaolinitic clay deposits in the country are either sedimentary or residual
in origin and are usually associated granitic rocks. Occurrences of kaolin have been
recorded in different parts of the country and specific abundant deposits have been
identified in parts of Enugu, Anambara, Kaduna, Katsina, Plateau, Ondo, Oyo, Ugun,
Bauchi, Sokoto, and Borno States. Of these reserves, about 800 million tones of
probable/proven deposits have been quantified. The locations of some kaolinitic clay
deposits are listed in the table below.
33
Table 1.4.10 Locations of Kaolin Deposits in Nigeria
S/N STATE LOCATIONS ESTIMATED
RESERVE
REMARKS
1 Kogi Agbaja
2 Niger Lavun, Gboko,Bida,
Patigi, Kpak
3 Kaduna Kachia , Manaraba-Rido 5.5 million tones Partial exploitation
4 Plateau Major porter Nahute,
Barikin-Ladi,Mangu,
Kanam
20 million tones Commercial
exploitatio
5 Bauchi Alkaleri, Ganjuwa,
Darizo, Misau, Karfin
20 million tones Commercial
eploitation
6 Yobe Fika (Turmi)
7 Borno Maiduguri (Gongulon),
Bui, Damboa
8 Edo All part of the state Large Yet to be exploited
9 Delta Aniocha, Ndokwu Large Yet to be exploited
10 Osun Irewole, Ile-Ife, Ede, Odo
Otin, Ilesa, Iwo
Partial exploitation
11 Katsina Kankara,Dutsen-ma,
Safana,Batsari, Ingawa,
Musawa, Mulumfashi
20 million tones Exploitation by
RMRDC/KSTG model
factory; Katsina kaolin
and ceramics Ltd. Etc.
12 Kano Rabo, Bichi, Tsanyawa,
Dawakin Tofa, Gwarzo
Not available Not available
13 Kebbi Danko, Zuru, Giro, Dakin
Gari, Illo, Kaoje.
Not yet quantified
14 Oyo Tede, Ado-Awaye Not yet quantified Exploitation by local
porter
15 FCT Kwali, Dongara
34
Table 1.4.11 Chemical Composition of some samples of Kaolin deposits
Oxide Yobe
1
Yobe
2
ozubulu Kankara Nahuta Darazo Abeokuta Ifon Akure
SiO2 45.70 47.01 60.0 45.90 46.80 51.82 43.12 48.03 45.90
Al2O3 35.02 36.17 26 39.60 31.82 32.92 36.12 33.20 39.60
Fe2O3 2.00 2.31 5 0.37 1.93 2.93 3.1 0.06 0.37
K2O 0.01 0.20 0.43 0.86 0.89 0.43
Na2O 0.03 0.12 0.05 0.80 0.07 0.05
TiO2 5 0.06 1.9 1.73 0.06
CaO 0.09 0.75 0.39 0.09
MgO 0.08 1.80 0.29 0.08
L.O.I 12.58 13.04 12.65
Source: Raw Material Research and Development Council (2010)
Bentonite
Bentonite belongs to the group of clays whose technical properties are controlled by
the proportion of montmorillonite, a sub-group within the smectitic clays. It is clay
derived from deposits of weathered volcanic ash. Bentonites are hydrated
aluminosilicates, which composed predominantly of the clay mineral montmorillonite.
They are composed of a 3-tier structure with alumina silica sheets’ sandwiched
between tetrahedral silica units. A simplified formula for montmorillonte is Al2O3.
4SiO2.H2O. The other minerals that could be found in bentonite in small content are
chrystobalite, biotite, chalcedony, calcite, pyrite, dolomite and plagioclase.
There are three principal types of bentonite namely:
35
I. Natural sodium bentonite or sodium montmorillonite;
II. Natural calcium bentonites or calcium montmorillonite; and
III. Sodium activated bentonites or sodium activated montmorillonites.
Natural sodium bentonite as the name suggests, occurs with sodium as the
predominant exchange cation. They are characterized by high swelling, high liquid limit
and high thermal durability. It is usually used for drilling mud.
The vast majority of the montmorillonites occurring in abundance worldwide is of the
calcium type and is referred to as calcium bentonite. Much lower swelling and liquid
limit values compared to natural sodium bentonite, characterize them. Calcium
bentonite is used as a bleaching agent in cooking oil industries, bleaching agent in
lubricant oil recycling, as a catalyst, absorber, filler, etc.
Bentonite has a wide range of industrial uses. The physical and chemical properties of
bentonite make it an important industrial mineral, which has widespread application in
various industrial sectors, listed as follows:
– It is used as foundry sand bond in iron and steel foundries and in iron ore
pelletizing in metallurgy; this is probably the largest use for bentonite;
– As insulator in civil engineering;
– As an efficient materials for drilling mud (because the gel-like suspension it
forms in water)
– As bleaching clay in oil refining; clarifying and decolourising;
36
– Filtering agent for clarifying wine, beer and treating waste water;
– Ingredient in cosmetics, animals feeds and pharmaceutical;
– Colloidal fillers for paints, and decolourising agent in food industries;
– As soil conditioner, carrier for insecticides/pesticides, coating for seeds and
mineral additive in agriculture.
– Additive to ceramic raw materials to increase plasticity and enhance the
strength;
– Fire retarding materials;
– As coating on some types of computer papers, and non-carbon required
multiple copy papers;
– As cracking catalysts, bleaching agents, fillers and as dissociating agents in
petroleum refining, and chemical industries;
– As water impedance, where it prevents seepage loss from reservoir, irrigation
ditches and waste disposal ponds.
Bentonite Deposits in Nigeria
Marine shale units that are highly enriched in montmorillonite are found in Nigerian
sedimentary basins. Notable among these are the Awgu shale in Eastern Nigeria, the
Imo shale that forms a belt across Southern Nigeria, the Fika shale in the Northeastern
parts, and the Dukamaje and Kalambaina formation in the North West. Many
37
of sectors of these formations are said to possess mineralogical compositions of more
than 80% montmorillonite. Most of the shale are enriched in calcium and mixed
montmorillonite, but sections of abound that are enriched in sodium. Most of the
occurrences are Cretaceous or recent in age.
Bentonite clays also exist in the North-east quadrat of Nigeria (Borno, Yobe, Taraba,
and Adamawa) where a probable reserve of more than 700 million tones has been
indicated. Similarly, over 90 million tones have been reportedly found in Afuze,
Ekpoma-Igunebon road, Ovibiokhuan and Okpebho areas of Edo State. Some
occurrences have also been reported in Abia, Ebonyi and Anambara States.
Clay mineral studies of the tertiary to Recent subsurface in Niger Delta have revealed
occurrences of bentonite as well as other non-swelling kaolinitic clays. Since the Niger
Delta opens to the sea, there is likelihood that the subsurface Niger Delta bentonite
may be enriched in sodium from the saline seawater.
Exploitation efforts aimed at commercial exploitation are going on in several localities
now, while some companies have actually started test mining. The table below shows
the location of bentonite deposits in Nigeria.
38
Table 1.4.12 Locations of Bentonite Deposits in Nigeria
S/N STATE LOCATION ESTIMATED
RESERVE
REMARKS
1 Kebbi Jega Not quantified Found in Benin
formation
2 Borno Gamboru, Marte, Ngala,
Dikwa, Monguno
700 million
tones
Product of clay
of quaternary
and tertiary
3 Yobe Ngala, Marte, Mongunu,
Danboa
Black cotton
4 Adamawa
/Taraba
Gujba (Mutai) Not yet
quantified
Deposits in
River Channel
5 Gombe Akko, Gombe, Yamaltu-
Deba
6 Anambara Awka Not yet
quantified
Need for more
investigation
7 Imo Orlu,Isu, Oru, Okigwe Inferred
reserve
estimates are
5.8-7.5 million
tones
Mining
activities are on
in some of the
locations
8 Abia Arochukwu,Umuahia,
Bende, Isiukwuato,
Ikwuano
Proven/inferred
reserves in 5.8-
7.5 mil. tones
Most deposits
required further
investigation
9 Ebonyi Ohaozara Products of
Asu River
Group shale
Source: Raw Material Research and Development Council (2010
Feldspar
Feldspar is a group of closely related, rock forming alumino-silicate minerals, which
contain varying proportions of potassium, sodium, and calcium. The word ‘feldspar’ is
39
derived from the Swedish word ‘fald’ meaning field and German word ‘Spat’ which is
said to refer to any transparent or translucent material which is readily clearable.
Feldspar is the most abundant of all minerals, comprising over 50% of the earth’s
crust. It forms the major constituent of the of most igneous and metamorphic rocks, as
well as the arkosic sediments. Commercial feldspar occurs in feldspar rich pegmatites
of alder granites. Feldspar are valued as raw materials that form a vital input in
ceramic, glass, paper, chemical, agricultural, pharmaceutical, paints, plastics, and
rubber industries.
The alkalis and alumina contents are the two properties of feldspar that make it
beneficial for industrial use. It is estimated that about 85.90% of feldspar produced is
consumed by the glass and ceramic industries, although the proportion varies from
country to country. Feldspar provides an inexpensive source of the alkali metals
(sodium and potassium), and alumina. In the ceramic industry especially in the
manufacture of white ware, feldspar is the second most important ingredient after clay.
For glass manufacture, feldspar is still one of the most important raw materials.
Out the use of feldspar as fluxes in the ceramic and glass industries, they are used as
fillers and extenders in the paints, chemical, plastic, and rubber industries. They also
used in the building/construction industries, where they can be used as decorative
stones and chipping respectively. At times due to their luster and colour, they may be
used as semi precious stones, and in the production of mild abrasives.
The Nigerian feldspars are very suitable for use in ceramics, paints, cosmetics, and
glass industries. However, for colourless clear glass sheets, the feldspar may require
40
processing to remove biotite. This may be done by manual hand picking of the chips
before grinding. Froth floatation benefication technique provides more practical means
of separating feldspar from associated mica and quartz minerals.
Feldspar Deposits in Nigeria
There are wide occurrences of feldspar in the granite and pegmatite rocks of Nigeria
but concentration of economic size is view. Feldspar occurs in the feldspar rich
pegmatite of the older granites around Egbe, Udiarehyu, Okene and Lokoja in Kogi
State; Osogbo in Osun State; Ijero-Ekiti in Ondo State; Abeuokuta in Ogun State;
Gwoza in Borno State and parts of Taraba/Adamawa State. Locations and chemical
compositions of some samples of feldspar are shown it the tables below:
Table 1.4.13 Locations of Feldspar Deposits in Nigeria
S/N STATE LOCATIONS ESTIMETED
RESERVE
REMARKS
1 Ogun Abeokuta,
Gbegbinlawo, Aiyedeti,
Jagunna, etc.
Reserve not
estimeted
More
investigation
2 Ekiti Ijero-Ekiti 3.76 million tons
3 Osun Oshogbo, Ilesha, Ede,
Ipole, Iwo, Atakumsa
etc
Not yet
estimated
Need further
investigation
4 Plateau Bassa, Mangu,
Pankshin, Langtan etc.
5 Niger Kontagoro,Shiroro,
Borgu
6 Kogi Osara, Okene, Egbe,
Lokokaja etc
Being exploited
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