CaSiO³ - This material varies in fiber lengths depending upon where it is mined.  Wollastonite found in parts of South America is relatively short, and has minimal reinforcing properties.  But it can be low in price, and judiciously used in extruded or rolled formulations where fiber orientation occurs it can be a useful ingredient.  Indian wollastonite fibers are longer and can be seen in dry mix formulas where they probably replace more costly glass fibers.  Moh hardness is 5 - 5½ which is about halfway between that of barytes and silica