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Imerys Group has made every effort to ensure that information provided on the Imerys website is accurate at the time of inclusion. However, there may be inadvertent and occasional errors for which Imerys Group apologises.

Imerys Group makes no representations or warranties about the information provided on its website or via hypertext links or any other item used either directly or indirectly from Imerys Talc’s website and reserves the right to make changes and corrections at any time, without notice. By accessing this website, you agree that Imerys Group will not be liable for any inaccuracies or omissions or any direct, special, indirect or consequential damages or losses, or any other damages or losses of whatsoever kind resulting from whatever cause through the use of any information obtained either directly or indirectly from or through Imerys Talc’s website and any decisions based on such information are the sole responsibility of the visitor.

No information contained in Imerys Talc’s website constitutes or shall be deemed to constitute an invitation to invest or otherwise deal in the shares or any other securities of our parent company, Imerys, or any other member of the Imerys Group and must not be relied upon in connection with any investment decision.

The above exclusions and limitations apply only to the extent permitted by law.

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Any information you have provided through this website will only be used by Imerys Group, and possibly its parent company Imerys, to answer your present enquiry. Where it is necessary, in order to answer your enquiry, the information you have provided may be passed to any Imerys Talc company worldwide. The information will not be passed to anyone outside the Imerys Talc or Imerys Group for any other purpose. By sending this information to us you are consenting to the personal information contained therein being transferred within the Imerys Talc, or potentially Imerys Group, worldwide and being processed for these purposes.

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How talc is formed

 

1 -  Yellowstone mine in Montana - USA - a magnesium carbonate derivative orebody


The talc results from the transformation of carbonates (dolomite and magnesite) in the presence of silica. The carbonates fix in-situ the magnesium needed to form the mineral, whereas the silica is provided by hydrothermal circulation. This reaction results in a talc which, depending on the composition of the parent rock, is either mineralogically pure or associated with minerals such as carbonates (both residual and reactional), quartz and chlorite. Deposits of this kind represent some 60% of world talc extraction and provide some of the whitest and purest talc ores. Our Yellowstone mine in Montana, USA, yields this type of talc.

 


2 -  Argonaut mine in Vermont - USA - a serpentinite derivative orebody


About 20% of present world production comes from the transformation of serpentinite into a mixture of talc and reactional magnesium carbonates. This ore, commonly called "soapstone", is always grey and never pure. To be used as an industrial mineral, it is often upgraded by flotation to increase the talc content and whiteness. This type of deposit is relatively common and widely distributed along ultra-mafic rock belts. Our deposit in Vermont USA is a serpentinite derivative orebody.


3 -  Trimouns mine, France - a silico-aluminious rock derivative orebody


Here, talc results from the transformation of siliceous rocks such as quartzite, which provide the silica needed for the mineral's formation. Magnesium is brought by the migration of hydrothermal fluids. If the parent rock has a silico-aluminous composition, e.g. pelitic schist or gneiss, chlorite can be formed in addition to the talc, the resulting ore being a mixture of both talc and chlorite. This type of deposit can be found in association with the magnesium-carbonate derivative type, as is the case of our Trimouns mine in the French Pyrenees. This kind of deposit represents about 10% of world production.

Talc is one of the common minerals in metamorphic rock. Although talc deposits can be found throughout the world in various geological contexts, economically viable concentrations of talc are not that common.

Talc deposits result from the transformation of existing rocks under the effect of hydrothermal fluids carrying one or several of the components needed to form the mineral MgO, SiO2, CO2. Tectonics plays a major role in the genesis of a talc deposit. It enables hydrothermal fluids to penetrate the rock, creating a micro-permeability that facilitates reactions in the mass. The size and shape of talc deposits depend upon the intensity of this hydrothermal activity which corresponds to the climate of a low temperature metamorphism. Pressure and deformations, both concurrent with and subsequent to this transformation, determine the crystallinity of the talc ore in the deposit. Talc deposits differ according to the parent rock from which they are derived.

There are four main categories of talc deposit: magnesium carbonate; serpentinite; silico-aluminous; and magnesium sedimentary orebodies - the last of these are not economically viable. These deposits yield a wide variety of ores that differ in terms of:

  • mineralogical composition,
  • color - measured in terms of whiteness or brightness,
  • crystalline structure (compact or platy).

These three parameters govern the specific nature of each commercial talc grade and what it will be used for.