General information and occurrence
Kaolinite clays called as refractory clays are an indispensable raw material for the production of aluminosilicate fire resistant materials. They are also used for the production of ceramic tiles and sanitary articles. Such clays originate in the result of wash down of outcropping and near-surface kaolinized rocks and a redeposition of kaolinite, connected with a separation of quartz grains and a marked improvement of fire resistance properties of that raw material.
The basic components of the refractory clays are kaolinite clays, characterized by a high plasticity and with the ability to form a ceramic body with a high mechanical strength. The fire resistance of such clays should be minimum of 1,650°C.
From the dozen or so documented deposit in Poland, there are only two exploited deposit of refractory clays: Rusko-Jaroszów (Dolnośląskie Voivodeship, Świdnicki County) and Borkowice-Radestów (Mazowieckie Voivodeship, Przysusuki county). The output from Rusko-Jaroszów deposit has been carried out for years, whereas the exploitation concession for Borkowice-Radestów deposit was issued in 2020.
Refractory clays deposits are presented on the map.
Resources and output
Table 1 shows the current state of exploration and development of the refractory clay resources.
The anticipated economic resources of refractory clays as of 31.12.2020 amounted to 54.08 million tonnes and decreased by about 0.06 million tonnes (0.11%) in comparison with 2019 due to the exploitation. The anticipated economic resources covered by the detailed exploration (in A+B, C1 categories) were equal 53.41 million tonnes. They accounted for 98.76% of the total anticipated economic resources.
Economic resources of refractory clays were equal 1.82 million tonnes accounting for 1.94% of the total anticipated economic resources and 28.89% of the anticipated economic resources within exploited deposits. The economic resources significantly increased in comparison with the previous year – by 0.77 million tonnes (73.33%) as the result of the deposit development plan approval for Borkowice-Radestów (+0.82 million tonnes) and the exploitation.
In 2020, the output of refractory clays was equal 63.34 thousand tonnes and increased by 20.46 thousand tonnes (47.71%) in comparison with the previous year (Table 2). The exploitation from Rusko-Jaroszów deposit grew by 12.46 thousand tonnes (29.06%) and the exploitation from Borkowice-Radestów deposit started (8 thousand tonnes). The exploited raw material may be used without any processing or after firing, as the so-called “fired clays”.
The figure given below shows changes in domestic resources and production of refractory clays in Poland in the years 1989-2020.
In The balance of prospective mineral resources of Poland the assessment of resources prospective for refractory clays in Poland was updated*. The main criteria adopted for determining the refractory clays deposits were: the deposit thickness (minimum of 1 m) and the overburden to the deposit thickness ratio (N/Z maximum of 2), in addition the qualitative raw materials parameters: fire resistance (minimum of 161 sP) and the grains >0.063 mm content (maximum of 10%). Taking these parameters into account, the prognostic resources of refractory clays were assessed to be equal 56.90 million tonnes (within the Udanin area in Doln ośląskie Voivodeship).>
Prepared by: Marcin Tymiński
* Galos K., 2020 - Iły biało wypalające się (white-firing clay, ball clay), kamionkowe (stoneware clay, ceramic clay) i ogniotrwałe (refractory clay, flint clay). In: Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31.12.2018 r. (eds. Szamałek K., Szuflicki M., Mizerski W.): 335-329. PIG-PIB, Warszawa [in Polish].