Chemistry of all types of Talc is as follows:
Chemistry: (1) (2) (3)
SiO2 60.06 62.16 63.37
Al2O3 1.60 0.88
FeO 1.74 1.41
MgO 30.83 30.86 31.88
CaO 0.40
H2O 5.02 4.92 4.75
Total 99.65 100.23 100.00
--Talc, when pure, has a composition of 31.88% of MgO, 63.37% of SiO2 and
4.75% of Water.
PHYSICAL AND CHEMICAL PROPERTIES OF TALC (SOAP STONE)
Hegman Grind*: 3- 6
Density (g/cm3): 2.7- 2.85
Specific Gravity: 2.6- 2.85
Oil Absorption: 30-55
Solubility in H2O: Insoluble
Appearance: White Powder, Grey, Green etc
Odor: None
Mohs Hardness @20°C**:1.0- 1.5
pH***: 8.4-9.4
Crystallography: Lamellar
G.E. Brightness: 85- 97
Refractive Index: 1.59- 1.60
* Hegman
Fineness of Grind: Device that measures the fineness of dispersion of a
pigment. A Hegman gauge is a device used
to determine
how finely ground are the particles of pigment (or other solid) dispersed in a
sample of paint (or other liquid).
** The Mohs
scale of mineral hardness characterizes the scratch resistance of various
minerals through the ability of a harder
material to
scratch a softer material. It was created in 1812 by the German mineralogist
Friedrich Mohs. The hardest known
naturally
occurring substance when the scale was designed, diamonds are at the top of the
scale.
***pH is a
measure of the acidity or Basicity of a solution. Pure water is said to be
neutral, with a pH close to 7.0 at 25 C (77 F).
Solutions
with a pH less than 7 are said to be Acidic and solutions with a pH greater
than 7 are said to be Basic or Alkaline.
Talc is also name as Soapstone, French Chalk and Steatite.
- - Soapstone refers to all massive gray to bluish or greenish Talcose rocks which generally have a slippery feeling and can be carved by hand.
- - French Chalk is a soft variety of Talc used for making cloth.
- - Steatite is a grade of Talc suitable for making electronic tube insulators.
COLORS OF TALC (SOAP STONE)
Talc Major Colors are: White, Grey, Green, Blue, Pink, Violet, Silver. It all depends upon the Talc's chemical composition, and what proportions of such elements as Aluminum, Iron, Manganese and Titanium may also be present.