One of the most important useful and widely abundant industrial minerals in the world is the clay minerals. Their applications in various industries are dependent on their properties. In this study, the mineralogical and physico-chemical properties of RahinSho (RC), Major Porter (MP), Wereng camp (WC), Kwi (KC) and Naraguta (NC) clay deposits in Plateau State, Nigeria were investigated to evaluate their potentials for some industrial uses. The x-ray diffraction studies revealed the kaolins as the dominant clay minerals in all the samples. The non-clay minerals found were quartz and muscovite. The chemical analyses by x-ray fluorescence also indicated that the silica (SiO 2) values of the samples ranged from (41.20 - 62.26)% while the alumina (Al 2O 3) range was (17.25 - 37.15)%. Some considerable amounts of impurities found were Fe 2O 3 (0.43 - 27.52)%, TiO 2 (0.05 - 3.28)%, K 2O (0.13 - 3.01)%. The oxides of Na, Ca and Mg were within acceptable limits in the clays for most purposes. The loss on ignition ranged from 4.30% - 12.43%. The physical properties investigated were particle size distribution that contained heavy clay-size materials ranging from 67.88% - 91.88%, plasticity index had range of values from 15.90% - 33.68%, and drying and firing shrinkages were 1.10% - 2.22% and 1.65% - 4.49% respectively. All the samples attained a temperature of 1500 °C without fusion except Naraguta clay that fused at 1300 °C. At the temperature of 1200 °C, RC, MP and WC clays retained their natural colours of white and near-white respectively, while KC and NC clays changed colours from orange pink and light brown to moderate pink and moderate reddish brown respectively. These results compare very well with several clays elsewhere. Based on these characteristics, the clays were observed to be potentially suitable for the production of paints, tiles, ceramics, refractories, sanitary wares and clay bricks. Minimal processing will increase the potential of RC and MP to meet up with specification for paper, fertilizer and/or pharmaceutical uses.
Clay deposits contain clay minerals, which are essentially hydrated aluminium silicates and are usually in association with non-clay minerals such as quartz, feldspar, mica, calcite, and so on [
Clay is an abundant raw material. Its exceptional and some specific properties lead to various industrial applications that depend also on its dispersions and rheological properties, the presence of organic materials and impurities, type and amount of exchangeable ions and soluble salts, and textural properties [
The industrial utilization of a clay deposit depends on its geological, mineralogical, chemical and physical properties. The assessment of economic potentialities of a clay body must involve the evaluation of the separameters [
Numerous studies exist on clay deposits that are widely spread in Africa and especially Nigeria [
The results of this characterization shows that the samples of NC and KC cannot be used as refractory clays but suitable for the production of building bricks and sewer pipes while RC, MP and WC suggests their applications in the paper, paint, ceramic, sanitary and tile industries.
Clay samples were collected from five different locations inthe Upper part of Plateau State, Central Nigeria. RahinSho and Major Porter deposits are located in Barkin Ladi, Kwi and Wereng Camp clay deposits are in Riyom, while Naraguta deposit is located in Jos North Local Government Area as shown in
5 kg of fresh samples in lump form were obtained randomly from ten different points within each deposit from underground local mines pit at the depth of 10 - 20 cm. The samples were air-dried for several days and crushed using a set of Denver crushers by Denver Equipment Co. England. Each crushed sample was thoroughly mixed, coned and quartered. Two opposite composite representatives were obtained and consequently milled and pulverized. These were packaged in small polyethene bags as representatives of the samples for the required tests [
X-ray diffraction
The identification of clay minerals of each clay sample was carried out using a Panalytical BV Empyrean PW 1800 X-ray diffractometer. All pulverized samples of (1.5 µm) size were oven-dried and about 0.5 g of each was mounted and analyzed using a copper (Cu) target radiation at 45 KV and 20 mA at the scan speed
of 2˚ per minute. The interpretation of the diffractograms obtained for each sample was done by comparing the peaks with those of standard minerals [
X-ray fluorescence
The chemical compositions of the pulverized samples were determined by Energy Dispersive X-ray Fluorescence (EDXRF) of the model PW4030 X-ray photometer that uses a rhodium anode tube. The sample film was placed firmly in a waxed and gold plated sample holder. The Energy Dispersive patterns were obtained with the help of a computer attached to the instrument and each compound recorded in percentage [
Loss on ignition
Loss on ignition was determined according to the Lechler and Desiletes method, [
Clay pH
The clays pH were determined using the Rex pH Meter (model pHS ? 25) and the procedure adopted according to [
Plasticity index of clay samples
The Atterberg plasticity method prescribed by [
Particle-size analysis
The particle size test was carried out by using the standard Hydrometer method [
The hydrometer was inserted into the mixture in the cylinder and the readings were taken after interval of 40 seconds twice. After 2 hours, another hydrometer reading and temperature were recorded. After 40 seconds and 2 hours, all the sand and silt particles would have settled and only clay will remain in suspension. The percentages silt and clay were then calculated and the interpretation of result was made by using a textural triangle.
Drying and firing shrinkage of clays
The clay drying and firing shrinkages were determined from brick bars prepared using a mechanical hydraulic press (model D-7064 Paul Weber) with its accessory moulds and the method adopted was [
Refractoriness of clay samples
Fired clay bricks were used to estimate the refractoriness of the clay samples according to the procedure by [
Colour test of clay samples
The colour of the clay samples were determined by using the American Rock-Colour Chart Test. The colours of both the raw and fired clays were ascertained by comparing with that of the chart based on the Munsell charts plot according to the method [
The mineralogical composition of the clays determined using X-ray powdered diffraction is presented in
Minerals (%) | RahinSho Clay | Major Porter Clay | Wereng Camp Clay | Kwi Clay | Nara-guta Clay | Reference clays | |||
---|---|---|---|---|---|---|---|---|---|
*Ibadan Clay | *Kan-kara Clay | **China Clay | ^NAFCON Recommended | ||||||
Kaolinite | 56.24 | 41.40 | 98.11 | 87.99 | - | 91 | 96 | 85 | 85 |
Dickite | - | - | - | - | 17.93 | - | - | - | - |
Illite | - | - | - | - | - | 3 | 3 | 15 | 3 |
Quartz | 39.70 | 30.45 | - | 12.01 | 82.07 | 6 | 2 | Tr | 4 |
Muscovite | - | 28.16 | - | - | - | - | - | - | - |
Felspar | - | - | - | - | - | - | - | - | 2 |
Others | 4.05 | - | 1.89 | - | - | - | - | - | 8 |
Total | 99.99 | 100.01 | 100.00 | 100.00 | 100.00 | 100.00 | 99.00 | 100 | 98 |
* [
The results indicate that the samples were composed of different types of minerals. The kaolin group of clay minerals is most predominant, while the main non-clay minerals are quartz and muscovite.
Kaolinite type of mineral was found in RahinSho (RC), Major Porter (MP), Wareng Camp (WC) and Kwi Clay (KC) deposits, while the dickite type was found in Naraguta Clay (NC) deposits. The main non-clay minerals are quartz found in varying proportions in all deposits except WC sample and muscovite found only in MP sample.
Clays are particularly noted to contain many mineral types, and are very diverse in composition. Many of their properties depend on the nature and amounts of the various minerals present. The analysis of the clay samples in
Quartz and muscovite are found in high proportion in these clays and this indicates that all the clay samples formed at the deposits are either of residual weathering or hydrothermal formation. Such clay minerals are formed as alteration products associated with geothermal areas and hot springs, and as aureoles around hydrothermal ore deposits This type of kaolin clays undergo little or no transportation and usually contain a much larger proportion of primary minerals [
The proportion of dickite, one of the two well-formed of all kaolin mineral found in NC sample was quite low (17.93%). The occurrence of this mineral type is not common but mainly formed as a product of acid hydrothermal fluids. It is also occasionally found in iron beds as a white powder in cavities and center of noodles [
The result of the chemical analysis summarized in
The high amounts of SiO2, Al2O3 and LOI define the clay samples as hydrated alumino-silicate type of minerals [
In most samples, SiO2 and Al2O3 are the distinctive major constituents. The only exception is observed with NC clay that has very high Fe2O3 of approximately 28% and the Al2O3 content (17%) is much lower than in other samples. This explains the probable reasons for the low value of the clay mineral of Naraguta clay shown in
Oxides (%) | RahinSho Clay (RC) | Major Porter Clay (MP) | Wereng Camp Clay (WC) | Kwi Clay (KC) | Naraguta Clay (NC) |
---|---|---|---|---|---|
SiO2 | 62.26 | 55.10 | 50.15 | 46.48 | 41.20 |
Al2O3 | 29.44 | 34.73 | 37.15 | 31.12 | 17.25 |
Fe2O3 | 0.43 | 1.39 | 1.93 | 5.54 | 27.52 |
TiO2 | 0.05 | 1.54 | 2.82 | 3.10 | 3.28 |
Na2O | 0.13 | 0.23 | 0.08 | 0.12 | 1.17 |
K2O | 2.19 | 1.97 | 0.13 | 0.33 | 3.10 |
CaO | 0.46 | 0.43 | 0.06 | 0.23 | 0.33 |
MgO | 0.33 | 0.15 | 0.07 | 0.14 | 0.57 |
LOl | 4.30 | 5.22 | 8.38 | 12.43 | 5.13 |
The results of the chemical analysis show that the clay samples have SiO2 content in the order RC (62.26%) > MP (55.10%) > WC (50.15%) > KC (46.48%) > NC (41.20%). These values except for KC and NC are slightly above the ideal SiO2 value of pure kaolinites (46.54%) [
The Al2O3 content also follows the order: WC (37.15%) > MP (34.73%) > KC (31.12%) > RC (29.44) > NC (17.25%). WC, MP and KC samples reflect values close to that of pure kaolinite with 39.50% which also indicates the quality of the pure clay minerals [
The analysis also reveals the presence of some significant impurities such as the oxides of Fe, Ti (coloring agents) and the oxides of Na and K (fluxing agents). The amount of Fe2O3 in some of the samples were high and are in the order: NC (27.52%) > KC (5.54)> WC (1.93%) > MP (1.39) > RC (0.43%). High amount of Fe in clays effect an alteration in their color, reduce the refractoriness which act as weak fluxes and may form scum and visible spots on burnt clay bodies [
The oxide of Ti follows similar trend as Fe2O3 in the order NC > KC > WC > MP > RC. Minerals of titaniaact as feeble fluxes at temperatures of 1500˚C and above [
The alumina content of RC (29.34%) is similar to Ball Clay Tennessee (29.44%) while the content of silica for RC (62.26%) is slightly higher than for Ball clay Tennessee (53.96%). The metal oxides of these clays are also similar as shown in
Also WC with 37.15% alumina and 50.15% silica is similar to China clay Qty having 37.65% alumina and 46.88% silica shown in
The results of physical and firing characteristics of the clay samples are presented in
The clay content for WC and KC samples are close to, while MP, RC and NC are higher than the calculated mineralogical composition shown in
Sample Clays | Particle Size (%) | Plasticity (%) | Shrinkage (%) | pH | Colour | Refractoriness (˚C) | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Clay | Silt | Quartz | LL | PL | PI | Drying | Firing | Natural | Fired 1200˚C | |||
RahinSho Clay | 67.88 | 24.00 | 8.12 | 57.30 | 25.45 | 33.68 | 1.10 | 1.65 | 6.0 | Whiter than N9 | Whiter than N9 | >1500 |
Major Porter Clay | 73.88 | 18.00 | 8.12 | 45.38 | 29.48 | 15.90 | 1.10 | 2.23 | 6.1 | White N9 | White N9 | >1500 |
Wereng Camp Clay | 91.88 | 6.00 | 2.12 | 61.15 | 44.05 | 17.20 | 2.23 | 4.99 | 5.6 | Near White 5YR 8/1 | Near White | >1500 |
Kwi Clay | 84.88 | 14.00 | 4.12 | 63.90 | 28.60 | 33.30 | 1.14 | 2.40 | 5.2 | Moderate Orange Pink 5YR 8/4 | Moderate Pink 5R 7/4 | >1500 |
Naraguta Clay | 49.88 | 43.00 | 7.12 | 48.03 | 23.50 | 24.53 | 2.22 | 3.30 | 6.4 | Light brown 5YR 5/6 | Moderate reddish brown 10R 4/6 | Fused at 1300 |
LL = Liquid Limit; PL = Plasticity Limit; PI = Plastic Index.
Oxides (%) | China Clay Qty | Fire Clay Yorkshire | Building Brick Clay Glacial | Flint Clay Negev | Ball Clay Tennessee | (Belpahar Refractory Clay India | Residual Kaolin Ibadan | Kankara Clay Katsina |
---|---|---|---|---|---|---|---|---|
SiO2 | 46.88 | 56.60 | 60.10 | 36.00 | 53.96 | 50.00 | 63.20 | 44.09 |
Al2O3 | 37.65 | 26.90 | 17.10 | 47.00 | 29.34 | 31-33 | 25.61 | 38.67 |
Fe2O3 | 0.88 | 1.70 | 5.40 | 1.20 | 0.98 | 3.5 | 1.52 | 1.13 |
TiO2 | 0.09 | 1.30 | 1.20 | 3.00 | - | 1.38 | 0.22 | 2.21 |
Na2O | 0.21 | 0.22 | 0.70 | 0.30 | 0.12 | 1.36 - 2.0 | 0.24 | 0.36 |
K2O | 1.61 | 1.26 | 2.70 | 0.30 | 0.28 | 1.75 | 0.52 | |
CaO | 0.03 | 0.20 | 3.70 | 0.20 | 0.37 | 0.61 | 0.10 | 1.20 |
MgO | 0.13 | 0.30 | 2.80 | 0.20 | 0.30 | 0.38 | 0.05 | 0.15 |
LOI | 8.00 | 1.26 | 6.40 | 13.00 | 14.01 | 9-14 | 13.50 | 14.43 |
Source: [
Oxide % | Plastics | Paints | Rubber Paper Textile | Ceramics | Refractory Bricks | Brick Clay | Tiles | Sanitary Wares | |
---|---|---|---|---|---|---|---|---|---|
SiO2 | 45.78 | 45.30 - 47.90 | 44.90 | 45.90 | 67.50 | 51 - 70.00 | 70.00 | 54.00 | 46.0 |
Al2O3 | 36.46 | 37.90 - 38.40 | 32.35 | 33.50 - 36.10 | 26.00 | 25.44 | 19.00 | 30.00 | 31.00 |
Fe2O3 | 0.28 | 13.40 - 13.80 | 0.43 | 0.60 | 0.50 - 1.20 | 2.40 | 1.60 | 1.40 | 1.10 |
TiO2 | - | 13.80 | - | 0.03 | - | 1.60 | 1.20 | 0.90 | |
Na2O | 0.25 | 0.20 - 0.35 | 0.14 | 1.60 | 1.50 | 3.50 | 0.5 | 0.50 | 0.40 |
K2O | 0.25 | 0.40 - 1.00 | 0.28 | 1.60 | 1.10 - 3.10 | - | 2.0 | 3.10 | 2.20 |
CaO | 0.50 | 0.03 - 0.25 | Tr | 0.50 | 0.30 | 0.20 | 0.2 | 0.30 | 0.40 |
MgO | 0.04 | 0.20 - 0.30 | Tr | 0.40 | 0.19 | 0.70 | 0.4 | 0.40 | 0.40 |
LOI | - | 12.40 | 5.40 | 8.80 |
Source: [
The plasticity index of the clay samples ranged between 15.90% to 33.30% (
The average liquid limit ranges from 45.38% to 63.90%. The values for NC and MP are 48.03% and 45.38% respectively. This shows that the clays can be worked through limited range of water content which is a vitalproperty in the ceramic and paper industries, where the behaviour of the clay-water mixture is important [
The results of the drying and firing shrinkages for all the samples in
The colour determination on the natural and fired clays is important in certain industries and it is also an essential requirements. Most kaolin clay deposits like China clays occur naturally as white, while others as fired white. Deviation from that is an indication of the presence of some impurity materials such as iron, cobalt or copper compounds [
The refractoriness of the samples except NC is as high as 1500˚C and it’s an indication of a good refractory property. Clays that could be used as fireclays must not fuse below 1500˚C and must be one above 1600˚C [
Comparison of the clays mineral compositions with some well-known clay deposits (
Also, a comparison of the clay samples in terms of their chemical compositions with some selected indigenous and foreign clays (
The chemical compositions of the clay samples in
The results of the mineralogical, chemical and physical properties show that all the samples are suitable for various industrial uses. The proportion of the kaolinite for Wereng camp and Kwi clays met the standard specification for kaolin by NAFCON. The chemical composition as well as the physical characteristics also revealed that these clays compare favorably with the specifications of some industrial and reference clays. Each sample deposit has industrial potentials. The naturally white colour of RahinSho and Major Porter clays make them suitable for paper, paint, rubber/plastic, white-wares (sanitary/dinner wares) and refractories productions. Also processing RahinSho and Major Porter to remove sand, Fe, Ti oxides to the desired levels and required size of the minerals could increase their application in paper, plastic/rubber; fertilizer production and even in pharmaceutical. Wereng camp clay with a near-white colour and high proportion of clay-size particles can be successfully used for paint, tiles, sanitary-ware and refractories production. Kwi clay deposit can be used for the production of low grade paint, sewage-pipes, clay bricks and pottery while Naraguta clay deposit’s is suitable in the production of clay bricks and sewer pipesdue to the high concentrations of Fe2O3, TiO2, K2O; moderate plasticity and low shrinkages.
The authors declare no conflicts of interest regarding the publication of this paper.
Jongs, L.S., Jock, A.A., Ekanem, O.E. and Jauro, A. (2018) Investigating the Industrial Potentials of Some Selected Nigerian Clay Deposits. Journal of Minerals and Materials Characterization and Engineering, 6, 569-586. https://doi.org/10.4236/jmmce.2018.66041