talc is a hydrated magnesium sheet silicate with the chemical formula Mg3Si4O10(OH)2 which theoretically
contains 31.9 % MgO, 63.4% SiO2 and 4.7 % H2O. In naturally occurring crystals, Mg may partially be
replaced by Fe, Al, Cr or Ni. talc's crystalline structure consists of a MgO/MgOH octahedral layer, which
lies between two SiO tetrahedral layers (see Fig. 1). The silicate layers are bonded together by weak Van
der Waal's forces. Thus the silicate layers sliding over one another cause the slippery feel of talc.
As the softest of all minerals with a hardness of 1 (according to Mohs' scale) talc
crystals generally occur in scaly-foliated aggregates. talc has a perfect basal
cleavage with slightly flexible but non-elastic platelets. It has a specific gravity
of 2.7 g/cm3, a pearly and/or greasy luster and is translucent to opaque.
The mineral's color ranges from white to silver white to pale green and is rarely pinkish or dark green.
Massive-compact talc is called Soapstone or Steatite.
As observed by Scanning Electron
Microscope the crystal habit of talc
corresponds to flattened tabular
crystals with a hexagonal cross-section.
(Click photo to enlarge)
The mineral's color ranges from white to silver white to pale green and is rarely pinkish or dark green.
From a chemical point of view talc is hydrophobic and organophilic.
Furthermore it is acid resistant, chemically inert and non toxic.
