Bentonite is a clayey mineral that originates by the transformation of volcanic glass and ash in an alkaline, most often an oceanic or lake environment, with the origin of clay-like minerals from the smectite group (mainly montmorillonite, beidellite and nontronite). The first to use the term bentonite was W.C. Knight, in 1887, who named bentonite after the town of Fort Benton in the American state of Montana. Bentonite is a clayey material of earthy structure, usually white, grey up to light-green in colour. Upon freshly cutting it, it has a waxy shine.
In terms of use there are two basic types of natural bentonite

  • Na bentonite - capable of absorbing a great volume of fluid and creating a viscous thixotropic suspension
  • Ca bentonite - with worse absorption and swelling, but with notable adsorption properties. With natrification its absorption properties can be significantly increased.

It is these special properties of smectite minerals in bentonite that give it an exceptional standing among other clays in terms of its uses. The swelling of bentonites upon contact with liquids, which can reach up to 12-fold growth of their volume, but also other properties is especially important. Physically and chemically bentonite fixes a whole line of substances and is used for their selection sorption, or separation. Another of its important properties is its viscosity, resulting from its huge internal surface (up to 900 m2/g), given by the large number of interstitial spaces (a large reaction surface) and, of course, by the many crystals in a volume unit. A typical property of bentonite is the high capability for base exchange, i.e. the ability to accept certain cations from a solution and substitute them for free Mg, Ca, or alkali. The significant rheological, sorption and colloidal properties of bentonites, or their combination, predetermines them for broad-spectrum use not only in industry but also in human areas (pharmacy, the food industry, cosmetics), environmental protection, etc.

The oldest and largest deposit of bentonite in Slovakia is in Stará Kremnička, the Jelšový potok (stream) location. Quarrying has been done here since 1974. At present, together with the deposits in Kopernica and Lutila, they form the most significant deposits in all of Slovakia. Smaller deposits are found in Bartošova Lehôtka, Dolná Ves, in Hliník n/Hronom, Zvolenská Slatina, Lieskovec and in eastern Slovakia, e.g. Fintice, Lastovce, Michaľany and the like. All domestic bentonites are practically Ca, or Ca-Mg bentonites and are predominately formed of the mineral montmorillonite. Bentonites are quarried via surface mining.

Bentonite is first of all an ecological natural raw material, which has irreplaceable and broad-spectrum uses in society:

  • Construction - a building and sealant material,
  • Protection and stability of corrosion of earth works,
  • Water constructions - the flushing of water works, sealing of dams,
  • Environmentalism - natural sealing geotextiles and materials, sealing mats, sorbents of hazardous materials (solids, fluids, gases), liquidation and stabilization of hazardous materials, or fluid and solid forms of contamination in industrial and other accidents. Construction and demolition of waste dumps, removal of environmental burdens and industrial accidents,
  • Borehole survey - drilling suspension, sealing of boreholes
  • Purification of wastewater,
  • Water management and purification of drinking waters,
  • Purification and filtration of wines, fluids and foods, refining of oils,
  • Pharmacological - production of human medicaments, powders, rubs and creams,
  • Cosmetics industry - powders, skin masks, makeup,
  • Agricultural - sorbent of herbicides and pesticides,
  • Production of feeds, medicaments and fertilizers in agriculture,
  • Production of bedding in agricultural production,
  • Raising of domestic animals - beddings,
  • Land improvement - soil sorbent for increasing soil fertility,
  • Casting and metallurgy - manifold uses,
  • Chemical industry - manifold uses, composites, catalysers, nanotechnology, analytical chemistry
  • Industrial plastics - manifold uses,
  • Production of coating materials and paints
  • Ceramics industry,
  • Production of cements
  • Paper-making, wrapping technology,
  • Textiles industry, etc.

Bentonite is a component of our everyday life and its essential need today.