WOLLASTONITE

Wollastonite a met silicate of calcium having the formula CaSiO2 and usually occurs as aggregated of bladed or needle like crystals. It is generally white in color, has a specific gravity of 2.8 to 3 hardness of 4.5 to 5 and melting point of about 1540 C.

Excellent dielectric properties, high resistance to heat chemical inertness and brilliant whiteness in powdered state are some of the qualities for which it is valued in various industries. Wollastonite is largely used in ceramic industry for making electrical insulations and glazed tiles. It is also used as an extender in paints, as paper coating, filler in plastics and rubber goods, fluxing material for welding rods.

There is no BIS specification for this mineral. However, the user industry prescribed their own specifications, which are enumerated below:

S. No.

Industry

Specifications

1.

Asbestos product

Wollastonite powder, 300 mesh size with CaSiO2
75 to 80%

2.

Ceramic

Wollastonite powder having expansion on firing,
size 250 mesh CaO 46-48%, SiO2 51=52%

3.

Electrode

Wollastonite powder size 250 mesh, CaO :
46-48%, SiO2 : 50%

Wollastonite Pct. Ltd., are the only producer of this mineral. They supply this mineral from their mines in Rajasthan of the following specifications various industries.

CaO

48.02%

TiO2

In trace

SiO2

48.77%

MnO

0.29%

MgO

0.06%

Na2O

0.02%

Al2O3

0.66%

K2O

0.11%

Fe2O3

0.43%

L. O. I.

1.68%

The party supplies the above grade with the following guarantees.

CaO + SiO2

96.5% (min.)

Al2O3

1.5%

Fe2O3

0.5% (max.)

L. O. I.

2.0% (max.)

Physical Requirements:

Sp. Gravity

2.9

Bulk density

855 Kg/M2

Oil absorption

25 30 lbs/100lbs

pH of 10% slurry

9.0

Solubility in water

0.0095 gm/100cc.

Melting point

1540 C

Future Trends: - Wollastonite is one of the latest minerals added to the list of industrial minerals marketed today. Its industrial application are growing gradually, over the past 30 years, it has become an important functional filler in a number of products including plastics, adhesives, pesticides, paints, and paper. This mineral was being tried as a possible substitute for asbestos all over the world. In India CBRI, Roorkee carried out research on substitution of asbestos by wollastonite in asbestos cement products, but the result so far are not very encouraging.

Only total reserves of Wollastonite have been tabulated and no classification according to end use could be given, as no date on the same was available in the inventory of Wollastonite. However, the end uses of Wollastonite have been mentioned with the reserves.

In India at present only one namely M/s Wolken (India) Ltd., are producing this mineral and supply the same to various industries with the specifications mentioned earlier page.

The reserves of Wollastonite may be classified as under:

Marketable Grade:

Chemical:

CaO + SiO2    

96.5% (min.)

Fe2O3

0.5% (max.)

Al2O3

1.5% (max.)

L. O. I.

2.0% (max.)

Physical Requirements:
Sp. Gravity                   -           3.9


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