Kaolin is mostly residual (primary), less often sedimentary (secondary) whitish rock, containing substantial amount of the kaolinite group minerals. It always contains quartz, and it may contain clay minerals, micas, feldspars, and other minerals, depending on the nature of the parent rock.
Kaolin originated mostly through weathering or hydrothermal alteration of various rocks, rich in feldspar, like granitoids, arkoses, gneisses, etc. These so-called residual kaolins could then be transported, thus originating sedimentary kaolins. The deposits are concentrated in feldspar rocks in which the kaolinization had occurred. The titanium-bearing kaolin originated of autometamorphic granites with high Ti-minerals content. World economic reserves of kaolin are estimated at about 12000 mill. tons.
Kaolin is used for various purposes and the required grade depends on the use. Most often it is used as a raw material in the ceramic industry - in production of porcelain and other clay ware, then as a filler in the production of paper, rubber, plastics and pigments, in production of refractory materials, and in cosmetics, pharmaceutical, food. Kaolin is also used in production of synthetic zeolites. Production of kaolin is often classified among production of clays.
Technological suitability of kaolin is assessed according to properties of the water washed kaolin. In the Czech Republic, kaolins are classified according to their use:
Kaolin for production of porcelain and fine ceramics (KJ); requirements: purity, rheological properties, strength after drying, pure white-fired colour (content of Fe2O3+TiO2 max. 1.6 %), refractoriness min. 33 PCE (1,730° C), screen residue on the screen 0.063 mm max. 2 %.
Kaolin for ceramics manufacturing (KK) has no specifically defined parameters and is used according to many ceramic recipes. Specially appreciated are white-fired colour, low content of colorant oxides, etc.
Kaolin used as fillers in paper industry (KP) is used both for fillers and coatings. Required properties are high whiteness and low content of abrasive particles. It is also used as fillers in production of rubber (requires minimum content of the so-called "rubber poisons" - Mn max. 0.002 %, Cu max. 0.001 % and Fe max. 0.15 %) and in plastics.
Titanium-bearing kaolin (KT) - contains over 0.5 % TiO2 and this type of kaolin occurs only in the Karlovy Vary region. Tests have proven in some cases a possibility to reduce TiO2 content by high intensity electromagnetic separation after which most of these kaolins can be used as KJ or KK grades.
Feldspar-bearing kaolin (KZ) contains higher amount of non-kaolinized feldspars and has been used mostly in ceramics for production of sanitary and technical ceramics.
All kaolin deposits in the Czech Republic originated by kaolinitic weathering of feldspar rocks. The major kaolin deposits are located in the following areas:
The Karlovy Vary region - parent rocks are represented by autometamorphosed and younger granites of the Karlovy Vary massif. This is the most important source of the top quality kaolins for the production of porcelain (KJ) or their eventual substitutes (KT). There are also deposits of the KK, less of the KP grades.
The Kadaň region - kaolins of this area originated from granulite orthogneiss of the Krušné hory crystalline complex. This kaolin is of the KK and KP grades.
The Podbořany region - parent rock is feldspathic sandstone of the Líně formation belonging to the Central Bohemian Permocarboniferous. There occur all aforesaid grades of kaolin here. The KJ kaolins are used as an additive into the Karlovy Vary kaolins in production of porcelain because of their rheological properties.
The Plzeň region - parent rock is represented by Carboniferous arkoses of the Plzeň basin. Kaolins of this area are of the KP grade (the largest reserves of the best quality kaolin), less of the KK grade, and only negligible part of the reserves is of the KZ and KJ grades.
The Znojmo region - these kaolins originated mostly from granitoids of the Dyje massif, less from the Bíteš orthogneiss of the Dyje dome of the Moravicum. These kaolins are of the KZ grade and less of the KP grade.
The Cheb basin - these kaolins originated through kaolinization of granites of the Smrčiny massif. There is only one deposit here (KK, KP).
The Třeboň basin - less important deposits, local kaolins originated from granites and biotite paragneisses of the Moldanubicum. Only ceramic kaolins (KK) are present.
All kaolin deposits of the Czech Republic are extracted by open-pit mining operations.
1 The Karlovy Vary region |
5 The Znojmo region |
2 The Kadaň region |
6 The Cheb basin |
3 The Podbořany region |
7 The Třeboň basin |
4 The Plzeň region |
8 Vidnava |
4. Basic statistical data of the Czech Republic as of December 31
Year |
1995 |
1996 |
1997 |
1998 |
1999 |
Deposits - total a) exploited Total reserves, kt economic proven economic probable subeconomic Mining output, kt a) Imports, t b) Exports, t b),c) |
71 10 1347694 252740 696312 398642 2800 3825 383498 |
71 11 1236135 282252 575381 378502 2798 5846 361858 |
74 11 1213915 279722 567527 366666 2982 10087 397720 |
66 12 1148848 276537 529649 342662 3049 16028 418948 |
65 11 1137513 263721 526900 346892 5183 13414 412178 |
The data of kaolin for production of porcelain and fine ceramics (KJ) and kaolin used us fillers in paper idustry (KP) have been stated separately regarding great varieties of technological use and prices.
1999 |
KJ |
KP |
Deposits - total Exploited a) Total reserves, kt economic proven economic probable subeconomic Mining output, kt a) |
28 4 196963 55087 73276 68600 382 |
22 6 409312 117211 206937 85164 4768 |
Note:
a) exploited deposits of KJ: Božičany - Osmosa - jih, Bystřice - Hájek, Jimlíkov, Krásný Dvůr; exploited deposits of KP:Horní Bříza, Chlumčany - Dnešice, Kralupy u Chomutova - Merkur, Lomnička - Kaznějov, Otovice - Katzenholz, Únanov - sever 3
5. Prices
Average prices of ceramic grade according to quality fluctuated between CZK 2000-3500 per ton in the domestic market. Average export prices were CZK 3600-3900 per ton. Paper filling kaolin has been sold at CZK 1600-1850 per ton and average export price has been CZK 3000 per ton. 13 414 t of kaolin and other kaolinitic clays (item 2507 of the customs tariff) were imported in 1999 (62.5% from Great Britain, 26.7% from Germany and 3.4% from Ukraine). Average import price was CZK 4 650 per ton. 412 178 t of kaolin and other kaolinitic clays were exported to Germany (35.9%), to Slovakia (13.4%), to Austria (12.8%), to the Netherlands (9.9%) and to Italy (6.0%) on average price of CZK 2 378 per ton.
Keramika Horní Bříza, a.s.
KSB s.r.o., Božičany
Chlumčanské keramické závody, a.s.
Kaolin Hlubany, a.s. Podbořany
Severočeské doly, a.s. Chomutov
Sedlecký kaolín, a.s. Božičany
Data on the world production of kaolin vary considerably; the statistics quote alternately dry or wet weight, raw or refined kaolin, exact figures on mined and produced volumes of saleable product or their estimates. In spite of these misleading facts we can estimate that the world production since 1984 in the range of 20 mill. tons per year, and in 1990 it obviously reached its top (27,760 kt). After the fall till 20 960 kt in 1993 the world production of kaolin has been on the increase. The major producing countries were as follows (according to the Welt-Bergbau-Daten):
Year: |
1995 |
1996 |
1997 |
1998 |
1999 e | |
Production, kt: |
23168 |
23623 |
24363 |
25000 |
25000 |
Main producers (1998):
USA |
36.9 % | |
Great Britain |
9.8 % | |
Germany |
7.4 % | |
Russia |
6.2 % | |
Brazil |
5.3 % | |
China |
4.0 % | |
Iran |
3.5 % | |
Colombia |
3.3 % | |
Czech Rep.. |
3.2 % | |
India |
2.2 % |
The Czech production of kaolin reached 5.0% of the world production according to the prelimitary datas in 1999.
Prices of kaolin on the world market - in spite of the lasting surplus of the supply - kept at the generally steady level. The Industrial Minerals magazine quotes each month prices of British and US kaolin. Average prices of traded commodities in GBP/t, FOT ex-Cornwall, GB at yearend were as follows:
A Kaolin refined, filler
B Kaolin refined, coating
C Kaolin refined, ceramic grade
D Kaolin refined, porcelain grade
Commodity / Year |
1995 |
1996 |
1997 |
1998 |
1999 |
A B C D |
62.50 97.50 60.00 102.50 |
62.50 97.50 60.00 102.50 |
62.50 97.50 60.00 102.50 |
62.50 100.00 60.00 102.50 |
50.00 72.50 62.50 105.00 |
In ceramic production a part of bodies is recycled. The increased recycling of paper little influences the kaolin consumption; when recycled mineral fillers and coating pigments are separated and slurry is discarded. The recycled paper - used mainly for newsprint and wrapping -uses little if any kaolin.
Depending on the use, the situation is as follows:
In production of porcelain, kaolin is irreplaceable.
In ceramic recipes, in some cases kaolin can be partially substituted by clays, talc, wollastonite, or mullite (also synthetic mullite), but mostly these substitutions are financially pretentious.
In production of paper (which consumes almost a half of the total production of kaolin), the possibilities for substitution are the highest - kaolin as a filler can be replaced by extra finely pulverized limestone, dolomite (also synthetic - precipitated), mica (muscovite), talc, wollastonite, etc.
In other cases, where kaolin is used as a filler (insulation materials, pigments, glass fibres), the situation in analogous.
In production of refractory materials and applications in the building industry, kaolin can be successfully substituted by other materials with adequate properties.