Abstract: Substantially pure, synthetic crystalline .beta.-wollastonite having a specific BET surface of 1-30 m.sup.2 /g made by first producing calcium silicate hydrates having a molar ratio of SiO.sub.2 :CaO = about 0.7 to about 1.3 by hydrothermal treatment of an aqueous mixture of a source of CaO and SiO.sub.2 and then annealing the calcium silicate hydrates at about 800.degree.C to about 1150.degree.C to convert them to the .beta.-wollastonite. The invention also encompasses the use of the calcium silicate hydrates and the .beta.-wollastonite in the manufacture of ceramic materials and glazings.