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| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Review |
Ian Wilson Consultancy, Withielgoose Farmhouse, Withiel, Bodmin, Cornwall PL30 5NW, UK
* E-mail: ian.r.wilson{at}btinternet.com
(Received 26 November 2003; revised 1 January 2004)
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ABSTRACT |
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 TOP ABSTRACT DEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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KEYWORDS: kaolinite, halloysite, China, ceramic, paper, clay, coating clay
There are many types of kaolin resources formed from different geological rock types, namely granites, volcanic and sedimentary sequences. The production of kaolin is estimated at 2.1 Mt in China which represented 8.4% of the world’s total of 24.9 Mt (million tonnes) in 2002 (Wilson, 2003). High-quality kaolin, which has undergone some beneficiation and processing, is estimated at 1.0 Mtpa (million tonnes per annum) with the main market being ceramics (75%), paper, paint and others (25%). China is the world’s leading producer of porcelain and sanitary ware of which kaolin is a major component. China is now the second largest producer of paper and paper board in the world and the demand for coating kaolin is increasing significantly with high-quality products having to be imported from Brazil and the USA. The kaolin industry, compared to elsewhere in the world, is very fragmented with no single company having a large market share. For each deposit, the particle shape, size and morphology, combined with the physical and chemical characteristics are important in determining their market utilization.
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DEPOSITS |
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TOPABSTRACTDEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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). The largest primary resources have been derived from the alteration of granitic rocks and their extrusive equivalents. These rocks were emplaced during the major Mesozoic cycle of magmatism, the Yanshanian, which affected a large area of the folded basement terrain of southern China. The Yanshanian was also an epoch for mineralization with tungsten, tin and rare earths of economic importance. A classification of Chinese kaolin deposits has been proposed by Zhang et al. (1982) as follows:
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II. Weathering residual
III. Weathering leaching
IV. Sedimentary – secondary
Many of the commercial deposits in China are those formed by the alteration of granitic-type rocks. Of recent importance are the developments of the sedimentary so called ‘hard kaolins’ which are found associated with coal measures in many Provinces in Northern China. For the purposes of this review a simple geological classification is proposed for the various types of clay found:
I. Kaolin/hallyosite derived from alteration of granitic type rocks
II. Kaolin/halloysite derived from alteration of volcanic type rocks
III. Sedimentary kaolin
Chinese kaolin deposits exhibit varying morphologies with many of the altered granites being a mixture of pseudo-hexagonal kaolinite (often formed in single crystals and in stacks) and tubular halloysite. A sedimentary kaolin from the Maoming Basin of Guangdong Province exhibits a typical pseudo-hexagonal shape with no evidence of a tubular phase. Some pure tubular halloysites from Guizhou Province, derived from volcanic solutions, are characterized by extremely low levels of titanium and iron. The particle shape, size and morphology, combined with the physical and chemical characteristics, are important in determining the end utilization and markets for the various clays. There has been a tremendous amount of detailed exploration and evaluation of kaolin deposits carried out in China (Lin, 1985; Ling, 1982; Lu, 1998; Yao, 1995; Zongjie, 1997). The local geological teams have a wealth of information with detailed chemical testing and some commercial evaluation.
Some of the main operating companies for hydrous kaolin in China are shown on a provincial basis in Table 1, with details of their location, geology (whether granitic, volcanic or sedimentary), production capacities and markets served (split between ceramics, paper and others – paint, rubber, plastics and other uses).
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DETAILS OF SELECTED DEPOSITS AND OPERATIONS |
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TOPABSTRACTDEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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The deposit is characterized by low Fe and Ti levels which make it very suitable for ceramics, especially porcelain. The clay is a mixture of halloysite and kaolinite (Fig. 2) with some illite (light greenish mineral resembling greisenized borders to quartz veins seen commonly in kaolin pits in Cornwall, UK) present along quartz-filled fractures. Officially, (Government Reports) Longyan is listed as having 53 Mt of the kaolinized matrix, of which 10 Mt has an Fe level of <0.30 wt.% measured as Fe2O3. When the kaolin is refined and processed, a reserve of 2 Mt of low Fe-bearing product is identified.
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. The three products show differing morphology but all are united in exhibiting low Fe. The strength (modulus of rupture) varies according to the particle size – the Longyan 325# product is very coarse, by comparison with the SSP and NZCC clays (Harvey & Murray, 1993), and hence has a poor strength. The 325# product is sold to various overseas companies in Japan, Taiwan, South Korea and Pakistan, amongst others. Selling is mainly through agents with the 325# product also marketed by WBB China as ML China Clay. The ex-works price for LKC 325# is in the US$ 100/t range which is far cheaper than competing materials. Since commencing operations in the late 1980s, Longyan has gained a significant position in the market place as a supplier of high-quality clay for use in high-quality porcelain. It is well known that several international kaolin companies have suggested joint ventures with Longyan Kaolin Company but so far none has succeeded. An announcement was made at the 1997 Industrial Minerals Conference in Shanghai that a joint venture had been formed between ECC International and the Jiuzhou Group but this did not materialize. Longyan represents a kaolin deposit that has been professionally evaluated and developed. To protect the deposit from indiscriminate development, the responsibility for all mining activity is with the Longyan Kaolin Company – they have the duty to supply other producers in the area with high-quality matrix with Fe levels <0.30 wt.% Fe2O3. Some of the matrix is sold direct to porcelain producers in China who utilize the sand in some of their body formulations.
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), some of which were exploited by the Zhanjiang Kelin Kaolin Company (formerly Zhanjiang Kaolin Development Company). However, these former operations have been closed for financial reasons and a new company, Zhanjiang Yuexin Mineral Industry has taken over the deposits and built a new plant near Portoe, 40 km north of Zhanjiang. Yuexin have three mines at Shandai, Tang Ya and Bei Tan. These are all kaolinized granites with the clay having a high yield (up to 45–50 wt.% at <45 µm) and a good brightness (84–89 ISO). Rheologically, the clay has a poor viscosity concentration due to the presence of a mixture of ‘stacky’ kaolinite and tubular halloysite which inhibits the flow of clay on paper.
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Mengson halloysite deposit, Yunnan Province.
This deposit is formed from the alteration of a granite known as alaskite, a feldspar-quartz assemblage with no mafic minerals. Yields of clay from the matrix are high at 33% and indicate the inherent high content of feldspar in the alaskite prior to alteration to halloysite. Mining is mainly underground with a series of adits. Reserves have been calculated at ~0.5 Mt of low-iron- and low-Ti-bearing material. Processing is simple but effective with matrix being fed into blungers where the sand settles and the clay overflows into a thickener. The clay is then passed through 4x8" cyclones where the resultant product is <200#. For a 325# product the clay is further fed through 5x3" cyclones. Clay is then filter pressed and sold as a cake after some drying in the sun. The resultant product is coarse (just 40 wt.% <2 µm) with 0.23 wt.% Fe2O3 and <0.01 wt.% TiO2 and is utilized at a ceramic porcelain factory, Jialida Ceramic Company in Dehua, Fujian Province and at the Dong Hong Clay Company in Guangdong Province.
Sedimentary kaolin
Maoming, Guangdong Province.
This is the most important domestic producing area (Fig. 3
). Resources have been put at 800 Mt by the 704 Geological Team but recent estimates of reserves have been put at 70–168 Mt. A geological survey of the Maoming Basin showing the main areas of kaolin mining is illustrated in Fig. 4. The reduction in resources available has resulted from the location of a major road right through the deposit and poor mining practice on the existing deposits. Good-quality kaolin to depths of 80 m has been proven by detailed exploration and drilling, but rarely is it mined to this level. Maoming at present has 26 processing companies with a total dry capacity (Spray Dryers to <1% moisture) of 90–100,000 tpa and filter cake (~35% moisture) of 340,000 tpa. Actual production at the present time is 75,000 tpa of dry powder and 200,000 tpa of filter cake. Some of the filter cake is sold to others for further beneficiation. The Maoming kaolin is characterized by a high brightness (often up to 89 ISO or 90–91 GE), fine particle-size distribution of 90 wt.% <2 µm and variable viscosity (Yuan & Murray, 1993). It can, with the correct processing, reach the level of a #1 USA kaolin and is certainly similar, apart from viscosity, to an imported USA #2. The kaolin is blocky in nature (Aspect Ratio 14–16) and has a well developed pseudo-hexagonal morphology (Fig. 5).
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. The kaolin is washed by monitors in the pit and the resultant kaolin is thickened and transferred, by road tanker, to the plant 2 km away. After cycloning and centrifuging (not always necessary) the clay is filter pressed and spray dried to <1% moisture. Most of the coating clay product at 90 wt.% <2 µm, with a brightness of >90 GE is sold in the Shandong area. The clay is taken to the nearby port of Shuidong where it is shipped to Qingdao for delivery to various paper mills in Shandong Province. The cost of transportation from Maoming to the customers in Shandong is approximately $25–30/t.
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Kaolin ore:$5–35/tonne
Filter cake (~35% moisture):$45–110/tonne
Dry powder (<2% moisture) for blade coating: $175–225/tonne
The production costs in the Maoming area are largely governed by the amount of chemical bleaching carried out but are generally ~$70–100/t giving a good profit at current price levels.
Hard kaolin
The location of some of the so called ‘hard’ kaolin deposits (generally known as Flint Clays) is shown in Fig. 1. Flint clay is generally associated with coal deposits. Flint clay deposits are mainly concentrated in northwest China with large reserves found in Shanxi, Sanxi, Inner Mongolia, Xinjiang and Henan Provinces. Flint clay products are also found in the coalfields in Shandong, Jiangsu and Anhui provinces. The reserves of these hard kaolins (flint clays) are put at 2000 Mt. The kaolinite rocks in the coal measures are often of very pure quality, apart from containing organics, and show diversity in nature and origin. The parent materials for these clays is the subject of much speculation and research. Typical analyses of kaolin rock from various Chinese coalfields are shown in Table 4. The kaolin is low in Fe and Ti. The kaolin found in these sequences is generally a well formed pseudo-hexagonal kaolinite with some irregular shapes and stacks of kaolinite. Pseudomorphs of feldspar and mica are also found. Due to its purity, but often containing some organic material, the kaolin is considered an ideal source for calcination. The Xuzhou deposit already supports a calcining operation with potential new calcining capacity being considered by the Yan Zhou Mining Group, in Zhou Cheng City, Shandong Province and a company near Shanghai who intend utilizing kaolin from the Huaibei (Anhui) coalfield. The calcined products from the present and future operations are likely to be suitable for paper and paint, replacing imported materials.
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The <1 mm fraction is micronized in a Raymond Mill to produce a 200# product. This is taken 3 km to the calcined clay plant. Here the 200# powder is slurried down with water to 25% solids and then passed through a Chinese-designed magnet at 1.1 Tesla which reduces the Fe level of the clay from 1.0% to 0.4 wt.% Fe2O3. The Fe-rich residues from the process are used in a special Fe-rich marine paint. The product from the magnet is passed through 1" and 3" cyclones to increase the solids level to 45%. The 45% solids material is then placed in a wet mill and ground with ceramic beads at 132 kWh/tonne with the addition of a dispersant. There are four grinders which work on a cascade method and the 200# material is reduced to a slurry with 90 wt.% <2 µm, 70 wt.% <1 µm and 30% <0.5 µm. This slurry is fed to a NIRO Spray Dryer where a powder with <0.5% moisture if produced. This is then milled to de-agglomerate any agglomerates formed during the spray drying. The powder is then fed into a 14 m longx2.5 m diameter Rotary Kiln at 950°C with a residence time of 2 h. The resulting calcined clay is further milled with the resulting powder product having a bulk density of only 0.18 t/m3. The clay is mainly destined for the paper market where it will be used in pre-coats for board and also as a filler in newsprint. Prices of such calcined clay is ~US$400/t. The characteristics of the Gold Rock Calcined Clay are shown in Table 5 and indicate a good brightness, low Fe and Ti and abrasion.
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. These deposits are very small and pockety and have generally been formed in volcanic rocks adjacent to limestone. The Al-Si rich solutions passing along fractures and faults have, on cooling, given rise to the very fine-grained halloysite (often 99 wt.% < 2 µm). Mining is carried out in small rabbit type holes followed by hand-picking, drying and further selection to give a Grade A halloysite with very low iron (< 0.2 wt.%) and titania (<0.02 wt.%). Some of these halloysites have a bluish tinge which disappears on drying. Production from the area is small, perhaps just 2000 tpa, and the halloysite is utilized, mainly by ceramic companies in China, to enhance fired brightness and to increase the strength of the porcelain body due to its inherent fineness and large surface area. Some of the halloysite is also exported to Japan and Korea for utilization in ceramics. Similar types of halloysitic clays are found in Turkey and in the Dragon Mine, near Salt Lake City, Utah, USA.
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). The zone of kaolinization follows the unconformity between the Jurassic volcanic rocks which are acid tuffs and breccias cut by porphyry dykes. The kaolin body has been produced by intense hydrothermal alteration of the acid volcanic rocks and associated dykes. Sericitization, silicification and pyritization accompany kaolinization. The present workings are now underground; the blocks of clay-rock extracted show contorted lenticular shapes and laminations which could be the result of tectonic deformation. Alunite nodules up to 50 cm in diameter occur in the clay rocks and fresh pyrite is also evident. There is a main set of northeast-trending fault structures which have helped govern the location of the kaolinized zones. The Suzhou Kaolin China Clay Company produces a wide range of products for the paper, ceramic, paint and other industries. The morphology of the clay is dominantly halloysite with the presence of more kaolinite nearer to the surface.
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MARKETS FOR KAOLIN AND HALLOYSITE |
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TOPABSTRACTDEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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. Overall, the top 20 companies showed a dramatic 32% increase from 2001 to 2002 with Shandong Bo Hui Paper Company increasing by 83% and Shandong Chenming Paper Holdings Ltd increasing by 80%.
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along with their paper-production capacities, paper types and kaolin and calcium carbonate demands. In addition to these companies, Oji Paper (Japan) has just announced a new plant at Nantong (near Shanghai) of 1.2 Mt total capacity, with a first phase of 0.6 Mt of coated paper by 2006 – the total investment is estimated at Yen 200 billion. Many major foreign companies have now invested in China with UPM-Kymmene and Stora Enso leading the European producers, YFuYu from Taiwan and Asia Pulp & Paper (APP), an Indonesian company, leading the way. South Korean companies are known to be looking at opportunities in China.
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The coated-paper and board capacity in Guangdong Province is 1.43 Mt with the majority at present being coated board. Shandong Province is an important producer and it is estimated that paper and paperboard production will reach over 6.0 Mt in 2003 (for comparative purposes, the total UK production for 2001 was 6.2 Mt).
For the four Provinces considered above, imports of Brazlian kaolin stand at 95,300 t (39%), US clays at 89,050 t (36%) and local Chinese kaolin 61,450 to (25%). The market for fine-particle-size, high-brightness kaolin for 2003 is estimated at 305,000 and is supplied by Brazil (100,000 t – CADAM Premier and PPSA Century kaolin), USA (90,000 t – Huber HG 90 and Hydragloss and Engelhard – Miragloss 90 and 91) and China (115,000 t – mainly Maoming coating clays). It is estimated that poorer-quality kaolin is also used in paper and board-coating accounting for another 95,000 tpa. This makes a total of up to 400,000 tpa of kaolin used in coating paper and board in China at the present time.
The paper and paperboard market in China is expected to double from current levels of 33 Mtpa in 2001 to 66 Mt in 2010 and 80 Mt in 2015. A main reason for the growth is that at present the apparent per capita use of paper/paperboard in China is only 29 kg as compared to 350 kg for the USA and 206 kg for the UK. The market for coating kaolin is expected to grow from the present level of 0.4 Mt to 0.83 Mt in 2010. This market will be largely met by imports from US and Brazil and perhaps a new project being developed in Australia. There is an urgent need for local Chinese resources to be identified and developed for this rapidly growing market.
Ceramics.
The annual demand in the ceramics sector has been around 600–700 Ktpa (thousand tonnes per annum) in the last few years, of which the beneficiated processed clay going to high-grade porcelain and glazing applications is in the order of 100 Ktpa. Recent developments in the Chinese ceramics market have been given by Fu (1997), Yao (1995), Yao & Hu (1996) and Zongjie (1997).
Sanitary-ware market.
According to Wu (1997) the market has a capacity of 49 Mp pa (million pieces per annum). The major production areas in China are Henan, Hebei and Guangdong Provinces with seven provinces accounting for 41 Mppa. At present there are some 385 sanitary-ware enterprises identified, of which 33 are of medium and large sizes. Between 1990 and 1995, imports of sanitary ware increased rapidly. However, since 1996 the level has decreased dramatically as domestic output has taken a far greater share of the market. Up to and during the 1990s a number of well known foreign sanitary-ware companies invested in China, with American Standard, Toto and Roca leading the way. The high quality produced by the foreign investors has raised the overall standard of sanitary-ware production in China which has also helped to reduce the imports. Local raw materials such as feldspar, silica sand and other constituents such as plastic clays are used, but some high-quality ball clay is still imported to maintain the quality of the slip. WBB Jiabei (now Asia Pacific Minerals) has set up a mining and processing company in Guangdong Province at Qingyuan to supply the local sanitary-ware industry with a product called Excel/Cast.
Tableware market.
The tableware market covers a wide range of product quality dependent on the raw material used and the firing conditions. A summary of some of the tableware types is:
Hard porcelain is made from a mixture of 50% China Clay, 30% China stone (petuntse) and 20% flint (or 20–30% each of quartz and feldspar). Biscuit firing is at a low temperature of 900–1000°C and then the body and feldspathic glaze are fired at a higher temperature of 1350–1400°C in a reducing atmosphere. Often called porcelaneous ware, this was first made in China, hence its common name china. Chinese porcelain is less vitrified (and therefore softer) than its modern European counterpart, which was developed in Germany in the early 18th Century. The ingredients melt and fuse into a dense strong body and the porcelain will allow bright light to pass through it (translucency).
Soft Porcelain is a vitreous translucent feldspathic whiteware, typically containing 50% kaolin and up to 50% feldspar, the remainder being quartz and is usually fired to a lower temperature than hard porcelain at 1220–1350°C in an oxidizing atmosphere. Glaze is applied and fired at 1000–1100°C.
Bone China is stronger than hard porcelain and has an ivory white appearance created by adding bone ash to the ingredients for hard porcelain. Bone China may be thought of as consisting of equal parts of a porcelain body recipe with bone ash. Typical ingredients are 50% animal bone, 25% china clay and 25% china stone. The biscuit-firing temperature is typically 1250–1280°C with glaze temperature in the range 1000–1100°C. Bone China became popular in England as the firing temperature is much lower than for hard porcelain, which meant that the English potters could use their existing methods and ovens. It also became popular as trade with China diminished due to the very heavy import duties on Chinese porcelain (108% in 1799). In China nowadays bone china is made with a typical composition of bone ash 50%, feldspar 15% and china clay 35%.
Size of market.
An estimate for tableware production in China is 10 billion pieces per annum. Of this, 40% is considered to be of medium to high quality. It should be mentioned that the value of a particular piece can be very low, for example a spoon can be purchased for US$0.19, a bowl for US$0.31 and a plate for US$0.15. The 4 billion ppa, it is estimated, would require 1 Mt of raw materials (based on 1 t = 4000 pieces). For the high-quality end of the market it is estimated that 50,000 tpa of Longyan type kaolin (low Fe, Ti and showing good translucency) is utilized.
The main tableware production areas are in Guangdong, Fujian and Hunan Provinces, their locations being due to their proximity to high-quality kaolin deposits.
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THE FUTURE |
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TOPABSTRACTDEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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The main trend of research in China for kaolin utilization has been in the development of kaolin products for high grade coating clay for paper and high grade clay for synthetic zeolite, paint, pharmaceuticals, chemical and plastic applications. It is envisaged that the annual demand for kaolin in the next decade will reach 3 Mt of which the demand for processed kaolin is expected to be 1.5 Mt. The need for enhanced processing technology and marketing skills for both domestic and overseas markets is seen as key to the further development of the Chinese kaolin business.
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ACKNOWLEDGMENTS |
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TOPABSTRACTDEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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REFERENCES |
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TOPABSTRACTDEPOSITSDETAILS OF SELECTED DEPOSITS...MARKETS FOR KAOLIN AND...THE FUTUREACKNOWLEDGMENTSREFERENCES |
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Fu D.Q. (1997) The recent development of China’s architecture ceramics and the raw materials consumption of the Industry. Industrial Minerals Shanghai Meeting, 1997.
Fujian Bureau of Geology and Mineral Resources (1989) The characteristics and genesis of kaolin deposits at Dongguanxia Mine in Longyan Pit, Fujian Province. Paper presented in the Symposium on ‘Exploration and formation of superlarge mineral deposits’, China, 199 pp. + 9 figures and 2 tables (in Chinese).
Harvey C.C. & Murray H.H. (1993) The geology, mineralogy and exploitation of halloysite clays of Northland, New Zealand. Pp. 233–248 in: Kaolin Genesis and Utilization (H.H. Murray, W.M. Bundy and C.C. Harvey, editors). Special Publication, 1. The Clay Minerals Society, Bloomington, Indiana, USA.
Li X. (1997) Exports of Chinese Industrial Minerals. Industrial Minerals Shanghai October Meeting, 1997.
Lin W. (1985) Current views on the geology and exploitation of kaolin in Fujian Province. Geology of Fujian, 2, 1–11.
Ling Y. (1982) The geological characteristics and composition of kaolin deposits in Fujian Province. Geology of Fujian, 2, 12–27 (in Chinese).
Lu W. (1998) Chinese Industrial Minerals (J. Griffiths, editor). Industrial Minerals Information Ltd., Surrey, UK.
Lu W. (1998) Chinese Minerals Directory, 2nd edition (J. Griffiths, editor). Industrial Minerals Information Ltd., Surrey, UK.
Wilson I.R. (2003) Kaolin Review. Mining Annual Review for 2003.
Wilson I.R., Halls C. & Spiro B. (1997) A comparison between the China Clay deposits of China and Cornwall. Proceedings of the Ussher Society, 9, 195–200.[GeoRef]
Wu D. (1997) The current situation and characteristics of the development of Chinese Ceramic Industry. Industrial Minerals Conference, Shanghai, 1997.
Yao S. (1995) China’s kaolin resources – a whistle stop tour. Industrial Minerals, July, 39–47.
Yao S. & Hu Y. (1996) Chinese kaolin – ceramic boom continues. Industrial Minerals, October, 77–83.
Yuan J. & Murray H.H. (1993) Mineralogical and physical properties of the Maoming kaolin from Guangdong Province, South China. Pp. 249–259 in: Kaolin Genesis and Utilization (H.H. Murray, W.M. Bundy and C.C. Harvey, editors). The Clay Minerals Society, Boulder, Colorado, USA.
Zhang Z., Lu D., Feng M., Feng B. & Jin T. (1982) Kaolin deposits of China. Pp. 719–731 in: Proceedings of the International Clay Conference, 1981, Sedimentology, 35. Elsevier, Amsterdam.
Zongjie Y. (1997) Current status and prospect of kaolin industry in China. China Kaolin Company, Suzhou, China. Industrial Minerals Conference, Shanghai 1997.
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