Kaolin
In Poland the name kaolin is referred to a white or yellowish soft clayey rock mainly built of minerals of the kaolinite group. Kaolin originates in the result of a weathering or a hydrothermal decomposition of igneous and metamorphic rocks rich in feldspars. From the origin point of view, kaolin can be divided into residual kaolin (primary – originated as an in-situ decomposition of a parent rock) and sedimentary kaolin (secondary – formed in the result of wash down of a weathered parent rock, transport and a deposition of weathering products in the other place.
The name of kaolin raw materials is referred to the Upper Cretaceous sandstones with a kaolinite cement occurring in the North Sudetic Depression. To this group of raw materials there were also assigned the deposit of basalts weathering products Dunino, originally documented as a halloysite raw material deposit. The re-assessing of the deposit resulted in re-classifying it to the kaolinite raw materials.
Deposits of kaolin raw materials in Poland originated in the result of a regional kaolinization of acid igneous and metamorphic rocks throughout vast areas in the foreland of the Sudety Mts. The process covered the Strzegom-Sobótka and Strzelin granitoid massifs as well as some parts of the Sowie Mts. and Izerskie Mts. In the Neogene the weathering processes gave rise to the origin of thick weathering covers. The kaolin deposits belong to two types – the residual kaolin or the kaolin sedimentary in nature, spatially related to the parent rocks. In both cases the deposits are located within the areas of the above mentioned massifs of granites and metamorphic rocks.
High-quality kaolin materials, that are those representing a fraction below 15 µm, are used in the manufacture of ceramics, rubber, polymers and fiberglass industries. In turn, coarser fractions find use in the making of recently fashionable ceramic wall and floor tiles of a „gres porcellanato” type, the production of which requires the washed kaolin with a very low content of coloring oxides (TiO2 and Fe2O3). The kaolin raw materials are also used for the manufacture of stoneware ceramics, white cement and fire-proof products.
Kaolin is being also obtained in the exploitation of glass sands (Biała Góra deposit) and foundry sands (Grudzeń-Las deposit).
Kaolin deposits occurence is presented on the map.
Table 1 shows resources and the state of development and exploration of kaolin raw materials in Poland.
Anticipated economic resources of kaolin amounted to 226.19 million tonnes in 2018 and decreased by 0.31 million tonnes in comparison with the previous year due to the exploitation and losses. There were not any new documentation or a documentation with recalculated resources of kaolin approved in 2018.
Anticipated economic resources of two exploited deposits amount to 54.02 million tonnes and account for 23.88% of total anticipated economic resources.
Economic resources, after the drop to the level of several hundred thousand tonnes (due to the formal issues – the lack of the deposit development plan for the exploitation area of Maria III and Maria III-1 deposits), increased again and amounted almost 46 million tonnes in 2018 due to the deposit development plan elaborated for Maria III-1 deposit.
In 2018, the output of kaolin raw materials increased by about 9% in comparison with the previous year and was equal 310.85 thousand tonnes, from which the exploitation of Maria III-1 deposit gave 309.50 thousand tonnes and of Dunino deposit only 1,350 tonnes of the raw material (Table 2).
The figure given below shows changes in domestic resources and production of kaolin in Poland in the years 1989-2018.
Prepared by: Agnieszka Malon
Table 1. Kaolin - million tonnes