What is Wollastonite?
Wollastonite is a calcium silicate that forms white blades, fibres and masses in contact-metamorphic limestones and is also important as an industrial mineral.
Mineralogy and structure
Reference formula: CaSiO3. Wollastonite is triclinic in the common 1T structure, while related polytypes and compositional substitutions occur. COD 9005777 is used as an exact structural reference for CaSiO3. Wollastonite is classified with silicates and has triclinic crystal symmetry. Typical hardness is 4.5–5 on the Mohs scale and specific gravity is approximately 2.8–3.1.
Colour, lustre and habit
Typical colours include white, colourless, grey, cream, pale green. The usual bladed, fibrous, massive habit and vitreous, pearly, silky lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Wollastonite forms in or is associated with skarns, contact-metamorphic limestones, calc-silicate rocks and silica-rich metamorphic zones. Important documented localities include Italy, the United States, Mexico, India, Finland, China and Canada.
White blades from a limestone contact zone
Wollastonite bridges cabinet mineralogy and industry: elegant white blades record metamorphism, while the same chemistry is valued in ceramics, plastics and construction materials.
Collecting and care
Protect fibrous specimens from abrasion and dust; use suitable controls for bulk industrial material and do not inhale powdered fibres.
