Chemical analysis, X-ray analysis, determination of specific gravity, various thermal tests and HCl-solubility test, etc. were conducted on 18 samples of wollastonite from Kiura, Oita Prefecture.
The following results were obtained;
(1) The main mineral component of the samples studied is wollastonite or parawollastonite, often containing quartz and calcite.
(2) The 18 samples of wollastonite examined have the following physical propertis: apparent specific gravity 2.8-3.0, bulk specific gravity 2.7-3.0, apparent porosity 0.4-3.3%, moisture content 0.2-1.1%. The chemical composition is SiO
2 43.60-59.09%, Al
2O
30.31-2.05, Fe
2O
3 0.25-1.07%, CaO 37.88-49.83%, MgO 0.39-2.24%, Ig. loss 0.54-9.29%.
(3) The thermal expansion up to 1000°C is 0.7-0.8%, and the thermal expansion curve shows nearly a straight line and there is not any unusual expansion. (as shown in Fig. 10)
(4) The transition of wollastonite (or parawollastonite) to pseudowollastonite begins at about 1200°C and almost ends at 1350°C. It seems that the transition temperature is determined by the kind and quantity of the impurities in the samples.
(5) It is possible to obtain higher quality wollastonite by acid treatment, but it must be treated with concentrated acid in order to separate calcite completely and in so doing the loss of wollastonite becomes considerably great.
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