top of page

Wollastonite - Jakobsberg Mine, Varmland, Sweden (Langban area)

From a report compiled by Howie G. - "Wollastonite is a chemically simple mineral composed of calcium and silica, with the chemical formula CaSiO3. It forms when impure limestones react with silica to produce wollastonite and carbon dioxide. Its structure is that of a long chain of silicate tetrahedra sharing common vertices.

Pure wollastonite is bright white. However certain trace metals substituting for calcium can cause other colors; gray, cream, brown, pink, green, or red. It is thought that the most common activator of fluorescence is Mn2+ substituting for calcium. When illuminated by shortwave UV light, the peak emission is at around 555 nm. There are also higher wavelength emissions most likely due to Fe3+ or Cr3+ substitutions.

China is by far the world’s leading source of wollastonite. Other significant producers include India and the United States. Currently the only commercially relevant wollastonite deposits in the US are in upstate New York. (more below)

Wollastonite - Jakobsberg Mine, Sweden

Wollastonite has several physical properties that result in its utility as an industrial mineral. It is essentially inert, and thus will not react with other components during or after manufacturing processes. When crushed, wollastonite breaks into needle-shaped (acicular) particles. As a result wollastonite reinforces plastics, paints, ceramics, and friction devices like brakes and clutches, analogous to the way steel rods reinforce concrete. Pure wollastonite is bright and white, and therefore useful as a white pigment.

The crystal structure and physical properties of wollastonite are stable to high temperatures, making it a good substitute for asbestos for thermal insulation applications. In ceramics wollastonite reduces gas entrapment and warping during firing and increases strength. It also contributes calcium in ceramic glaze mixes.

Use in the production of plastics is currently the leading market for wollastonite. The mineral is named after William Hyde Wollaston (1766–1822), a noted English physician turned chemist and mineralogist. Wollaston was a pretty big deal in diverse fields of science: he was the discoverer of the elements palladium and rhodium, his work helped pave the way for the development of new inventions such as the electric motor and the camera, and he did productive work in optics, physics and in physiology.

The definitive article on Franklin wollastonite, written by Richard C. Bostwick, is in The Picking Table, volume 45, number 2, 2004. Another interesting discussion, with major contributions by Mr. Bostwick and Mark Boyer, is in UV Waves, volume 42, March-April, 2012. An overview of the industrial uses of wollastonite, by Robert L. Virta, is found in the USGS Fact Sheet, FS-002-01. The best discussion of the fluorescence of wollastonite is in Modern Luminescence Spectroscopy of Minerals and Materials, by Michael Gaft, Renata Reisfeld and Gerard Panczer."

154 views0 comments
bottom of page