Abstract: Processes for the production of a building material in the form of woodstone panels or sheets which comprises preparing a mixture consisting essentially of between 30 and 40 parts by weight of finely divided calcined magnesite, a wood filler consisting predominantly of wood chips in an amount that is between 3 and 4 times, or between 1.05 and 1.8 times, the weight of the calcined magnesite, between 2 and 8, and preferably between 4 and 6, parts by weight of inactive diatomaceous earth, between 9 and 12 parts by weight of magnesium chloride in the form of an aqueous solution, and sufficient additional water to bring the water content of the mixture to between 30 and 60 parts by weight, compressing the said mixture into a desired shape by subjecting it to a pressure between 15 and 50 bars and hardening the said compressd mixture within a period of 20 minutes at a temperature between 120.degree. and 220.degree. C., and building materials produced by the said processes.