Bentonites and bentonitic clays
General information and occurrence
Bentonites are clayey rocks originated in the result of the transform (bentonitization) process of a volcanic glass occurring in the pyroclastic sediments such as tuffs and tuffites. The bentonites are built mainly of the smectite minerals group (with the minimum montmorillonite content of 75%) accompanied by other clayey minerals and relicts of a pyroclastic material. Related to the bentonites are bentonitic clays containing, along with smectite minerals, the larger amount of other clayey minerals.
The way of using rocks rich in the smectite group minerals depends on some common features such as: an ability to swell, their susceptibility to the dispersion of water, a high plasticity, their easy absorption of cations and organic substances from water solutions, their ability to form the thixotropic suspensions. Thanks to these features and due to the susceptibility to various modifications, there are more than 40 ways of utilization of these rocks, i.a.: in a foundry industry (as a component of foundry mass), in a chemical industry (for the production of fillers, sorbents, catalysts, decolorants, paints etc.), in a paper industry, a pharmaceutical industry, a cosmetic industry, a ceramic industry, in the engineering and hydro-technical works (a soil stabilization, waterproof screens, sealings), in an agriculture and as a component of drilling fluid. Most of bentonites in Poland are used traditionally in the foundry industry, the drilling and in a new, strongly developing hygienic sorbents market (for animals).
Primary bentonites (it means almost monomineralic montmorillonitic rocks with a small admixture of other minerals) occur very seldom in Poland. More common are various bentonitic clays with a relatively high content of non-clayey minerals. The group of bentonitic raw materials contains bentonitic weathering covers of basalts in the Lower Silesia region, bentonitic clays in the Upper Silesia region, bentonitic clays in the Carpathian Foredeep, bentonitic and zeolite-bentonitic clays and clay-schists in the Carpathians.
Resources and output
In 2020, anticipated economic resources of bentonitic raw materials amounted to 2,882.01 thousand tonnes. There are 3 deposits with an exploitation concession issued – Dylągówka-Zapady, Jawor-Męcinka and Krzeniów, located in Dolnośląskie Voivodeship. The output of the bentonites mantle rock of the basalt tuffs has been carried out only from Krzeniów deposit and for 20 years it has been maintaining within the range of 0.45-2.80 thousand tonnes per year. In 2020 the output was equal 0.92 thousand tonnes.
Table 1 shows the current state of identification and management of resources of bentonites and bentonitic clays in Poland.
The figure below shows changes in resources and output of bentonites in Poland in the years 1989-2020.
The total prospective resources of bentonitic raw materials amount to above 43.626 million tonnes and occur in Dolnośląskie (39.900 million tonnes), Świętokrzyskie (3.056 million tonnes) and Podkarpackie (0.670 million tonnes) Voivodeships*.
Prepared by: Dariusz Brzeziński
* Brański P., 2020 - Kopaliny bentonitowe i zeolitowo-bentonitowe (bentonite and bentonite clays, zeolite and zeolite clays). In: Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31.12.2018 r. (eds. Szamałek K., Szuflicki M., Mizerski W.): 362-364. PIG-PIB, Warszawa [in Polish].