Abstract: A process for the production of construction material comprising the steps of:1. heating soil to a temperature sufficient to destroy substantially the property of the soil to swell with changing levels of moisture without causing any of the soil constituents to melt, which temperature will normally lie between 500.degree. and 750.degree. C. depending upon the soil type,2. adding to the soil, either before or after the heating step, iron oxide in a finely divided form, to form a mixture and3. introducing into, or creating within, the mixture a solution of sodium silicate, such as by adding an aqueous solution of sodium silicate to the mixture or by adding to the mixture a strong solution of sodium hydroxide and a silica source.The construction material formed by the process, and articles formed thereform, form part of the invention.