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 south-western and central Poland, the only one exploited deposit of refractory clays (Rusko-Jaroszów), is situated in the Lower Silesian region – Dolnośląskie Voivodeship.
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 as of 31.12.2019 amounted to 54.14 million tonnes and decreased by about 0.05 million tonnes (0.09%) in comparison with 2018 due to the exploitation from Rusko-Jaroszów deposit.
The anticipated economic resources covered by the detailed exploration (in A+B, C1 categories) were equal 53.47 million tonnes and accounted for 98.76% of the total anticipated economic resources.
Economic resources of refractory clays were equal 1.05 million tonnes (1.94% of the total anticipated economic resources and 92.92% of the anticipated economic resources within exploited deposits). The economic resources decreased by 0.05 million tonnes (4.55%) in comparison with the previous year.
In 2019, the output of refractory clays was equal 42.88 thousand tonnes and decreased by 27 thousand tonnes (38.64%) in comparison with the previous year (Table 2). 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 1989-2019.
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 (wihitn 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.