Abstract: There is provided a process for replacing the magnesium oxide portion of a nature magnesium silicate with sodium oxide thereby to form sodium silicate which comprises melting a natural magnesium silicate and sodium carbonate at a temperature of from 1100.degree. to 1350.degree. C. until a clear melt is obtained, the molar ratio of sodium oxide derived from the sodium carbonate per mole of silica contained in the natural magnesium silicate being from 4:1 to 7:1, quenching and extracting said clear melt with water and separating the insoluble magnesium oxide from the solution containing predominantly sodium silicate and sodium hydroxide.

Abstract: There is disclosed a green moulded product suitable for preparing shaped fired units comprising (a) at least 55% to 99% by weight of non-calcined asbestos tailings, the remainder comprising (b) at least one of (i) a heat decomposable metal salt selected from sodium, potassium, lithium, calcium, barium, magnesium, aluminum and mixtures thereof in an amount of from 1% to 15% by weight, (ii) a natural aluminum silicate in an amount of from 1% to 30% by weight, and (iii) mixtures of (i) and (ii). The properties of fired units are such that they can be used as structural bricks, medium refractory bricks, firebricks, tiles and the like.

Abstract: Protoenstatite ceramic units are prepared by compressing units of a mixture of 55 to 80 parts by weight of uncalcined demagnetized asbestos tailings with 22 to 44 parts by weight of a source of silica and from 0 to 17 parts by weight of fluxing agents and firing the units at 1250.degree. to 1500.degree. C.