Wollastonite Powder (Calcium Metasilicate) CaSiO3

Product Description:

Wollastonite is a white to yellowish-brown naturally occurring mineral. It has good strength, firing characteristics and ability to reduce crazing. It is comprised chemically of calcium, silicon, and oxygen. Its molecular formula can be expressed as CaSiO3 or as CaO.SiO2. It is commonly referred to as calcium metasilicate according to the now obsolete classification of silicates as oxyacids of silicon, a salt of hypothetical metasilicic acid: H2SiO3. It has a theoretical composition of 48.28% CaO and 51.72% SiO2.

Natural wollastonite, however, may contain trace or minor amounts of various metal ions such as aluminum, iron, magnesium, manganese, potassium, and sodium. Any of these ions may partially substitute for calcium if they are present. Wollastonite is rarely found by itself, and ore zones in the major deposits contain 20-98% wollastonite. Associated minerals are most often calcite, garnet, and diopside.

Chemical Name:  Calcium metasilicate

Chemical Formula: CaSiO3 or CaO.SiO2 

Chemical Properties:

Theoretical composition:

CaO= 48.3% and SiO2= 51.7%.

The typical composition is:

CaO= 47.0% and SiO2= 50.0%

Physical Properties:

Various granulations are available. Primarily 10 X 100 mesh, 200 mesh X down and 325 mesh X down

Typical Applications

A source of silica and alkalis in the production of ceramics. It is used to produce wall tiles, semivitreous bodies, ceramic insulators and glazes, thermoplastics, adhesives, and ceramic-bonded abrasives.

Wollastonite has been found useful as a soil conditioner and an additive to plant fertilizer for its reactivity in acid conditions. As opposed to lime or calcite, it offers long-term protection against the acidification of soils. In some countries, wollastonite has also found use as an inert carrier for pesticides and insecticides.


Molecular Weight (g/mol.) 116
Density (lbs./solid gallons) 24.2
Specific Gravity 2.8- 2.9
Specific Heat @25°C (cal/g-°C)
Melting Point (°C) 1540
Boiling Point (°C)
G. E. Brightness 85-93
Thermal Conductivity @20°C (cal/s-cm-°C)
Mohs Hardness @20°C 4.5- 5.0
pH (aqueous solution) 9- 10
Crystallography acicular
Color white
Oil Absorption 22- 45
Refractive Index 1.63
Hegman Grind 4- 7