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Lhoist is a leading producer of lime, dolime or dolomitic lime, limestone, dolomite and other minerals, such as ball clay.

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What is lime?

Lime is the generic term often applied to lime, limestone and hydrated lime, although these products are chemically different as a result of processing and treatment.

  • Limestone (calcium carbonate - CaCO3) is present in large quantities in natural rock around the world.
  • Lime (calcium oxide - CaO) is an alkali and the result of the chemical transformation of limestone by heating it above 900°C, which requires energy (3.2 GJ/tCaO). Given its rapid reaction with water, calcium oxide, also called burnt lime, is often referred to as quick lime.
  • Hydrated lime (calcium hydroxide - Ca(OH)2) is a strong alkali formed when calcium oxide reacts with water. This reaction generates heat. Depending on the amount of water used, calcium hydroxide can either be a dry hydrate (dry powder), a paste (putty lime) or a liquid milk of lime also called lime slurry (dry suspension in water).
  • Precipitated calcium carbonate (PCC CaCO3) is a synthetic calcium carbonate. With special morphologies, it can be industrially produced through the reaction between calcium hydroxide and CO2.


What is dolime or dolomitic lime?

  • Dolomite (double carbonate of calcium and magnesium - CaCO2.MgCO2) is the result of a partial or full dolomitization of calcium carbonate  
  • Half-burnt dolomite (calcium carbonate & magnesium oxide - CaCO2.MgO) is formed when magnesium carbonate is only partially oxidized.
  • Dolime or dolomitic lime (calcium & magnesium oxide - CaO.MgO) is the result of the chemical transformation of double carbonate of calcium and magnesium by heating it above 900°C, which requires energy (2.935 GJ/t CaO.MgO). Like lime, dolime reacts with water. CaO’s affinity for water is higher than that of MgO.
  • Half-hydrated dolime (calcium hydroxide & magnesium oxide Ca(OH)2.MgO) is formed as the result of the reaction of dolime with water under normal conditions.
  • Hydrated dolime (calcium & magnesium tetrahydroxide - Ca(OH)2. Mg(OH)2) represents the completion of the hydration reaction carried out in pressurized reactors at temperatures of around 150°C.


What are minerals?

The various minerals that exist are used in a huge amount of industrial and agricultural applications. The minerals we operate in our mines include high-purity limestone and dolomitic limestone that serve the numerous markets with which we are doing business. 
Lhoist is also a key supplier of aggregate stone that is primarly used for roads and civil works. In our US facilities, we mine various specialty clays such as f.ex. ball clay, kaolin, sepolite, saponite and calcium bentonite.

  • Ball Clay is a hydrous alumina silicate derived from the kaolin family, formed from water-deposited sediment that has been chemically altered and mixed with sand, organic material and other constituents. Ball clay contains numerous minerals like kaolin, illite, mica, feldspare and quartz. Other "accessory" minerals and some carbonaceous materials are also present. It is quite rare and found in only very few places around the world.
  • Kaolin is the generic name for the mineral kaolinite, a six-sided plate-like crystal comprising oxides and hydroxyls of silicon and aluminum. Kaolin, also known as kaolinite or china clay, is a layered alumina silicate with a low shrink-swell capacity and low cation exchange capacity (CEC), formed by the chemical weathering of alumino silicate materials such as feldspar.
  • Sepiolite is a magnesium silicate with a unique lathe structure exhibiting extremely high internal and external specific surface area, low CEC, low specific gravity and the ability to disperse in both fresh and salt water.
  • Saponite is a magnesium smectite exhibiting large interlayer spaces between its sheet layer structure and a much higher CEC than sepiolite, but also with the ability to disperse in both fresh and saline water.
  • Calcium bentonite is a calcium-based altered clay exhibiting high base exchange capacity properties and a much lower tendency to absorb and swell than sodium bentonite.