Bentonites and bentonitic clays
Primary bentonites are produced in the result of a weathering of extrusive and pyroclastic rocks and usually display a parent rock structure. In turn, bentonite clays originate due to the redeposition of bentonite material and often yield fairly large admixture of foreign mineral components. Bentonite clays which form a weathering mantle developed on the Jawor-Męcinka and Krzeniów basalts were explored as mineral deposits accompanying those of basalts.
Rocks rich in smectite group minerals have some common features such as: an ability to swell, their susceptibility to the dispersion of water, their easy absorption of cations and organic substances from water solutions. Thanks to these features, there are more than 40 ways of utilization of these rocks, i.a.: a foundry industry (as a component of foundry mass), a chemical industry (for the production of fillers, sorbents, catalysts, paints etc.), a paper industry, a pharmaceutical industry, a cosmetic industry, a ceramic industry, in engineering and hydro-technical works, in an agriculture and as a component of drilling fluid. Most of bentonites in Poland are used in the foundry industry, the drilling and in a new, strongly developing hygienic sorbents market (for animals).
In Poland typical bentonites, i.e. containing more than 75% montmorillonite, occur very seldom. More common are bentonite clays, such as:
- bentonite weathering cover of basalts in Lower Silesia,
- bentonite clays in Upper Silesia,
- bentonite clays of southern fringes in the Holy Cross Mts.,
- bentonite clays in the Carpathian Mts.
In 2017, anticipated economic resources amounted to 2,883.43 thousand tonnes. There are two deposits with an exploitation concession approved – Jawor-Męcinka and Krzeniów (Dolnośląskie Voivodeship). The output of the bentonites mantle rock (an accompanying raw material) of basalt tuff has been carried out only in Krzeniów deposit and for more than 10 years it has been maintaining at the level of 0.45-2.80 thousand tonnes per year. Nevertheless, in 2017 the exploitation has not been carried out from any of these deposits.
Table 1 shows the current state of identification and management of resources of bentonites and bentonite clays in Poland.
At present, the only active bentonite mine is that in Krzeniów where accumulations of bentonite clays form a deposit accompanying that of basalts (Table 2).
The figure below shows changes in resources and output of bentonites in Poland in the years 1989-2017.
Prepared by: Dariusz Brzeziński