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