Process for preparing a rigid porous mineral foam, comprising the following steps: (i) preparing a suspension loaded with mineral particles and/or fibres, by mixing together: - an aqueous solution of at least one alkali metal silicate, an alkali metal aluminate, or mixtures thereof, with - mineral particles or fibres that are at least partially insoluble in the aforementioned solution, - optionally, at least one functional molecule; (ii) preparing a foam by dispersing a gas in a second aqueous solution comprising: - at least one natural or synthetic foaming agent of animal or plant origin selected from the group comprising egg white, lecithins, and the natural or synthetic proteins, optionally hydrolyzed, such as serum proteins, in particular albumin, caseins, halogenated proteins, or a mixture of the aforementioned foaming agents, and - optionally at least one surfactant that is different from the foaming agent used in said solution; (iii) preparing a foamy mixture by mixing the aforementioned suspension obtained in step (i) and the aforementioned foam obtained in step (ii); (iv) stabilizing the foamy mixture obtained at the end of step (iii) to obtain said rigid foam, said foamy mixture being stabilized by heating to a temperature between 30°C and 200°C, by injecting CO 2, by adding dry matter powder or metal powder, or by adding weak acids, organic esters, alkylene carbonates or acetic esters. (i) preparing a suspension loaded with mineral particles and/or fibres, by mixing together: - an aqueous solution of at least one alkali metal silicate, an alkali metal aluminate, or mixtures thereof, with - mineral particles or fibres that are at least partially insoluble in the aforementioned solution, - optionally, at least one functional molecule; - an aqueous solution of at least one alkali metal silicate, an alkali metal aluminate, or mixtures thereof, with - mineral particles or fibres that are at least partially insoluble in the aforementioned solution, - optionally, at least one functional molecule; (ii) preparing a foam by dispersing a gas in a second aqueous solution comprising: - at least one natural or synthetic foaming agent of animal or plant origin selected from the group comprising egg white, lecithins, and the natural or synthetic proteins, optionally hydrolyzed, such as serum proteins, in particular albumin, caseins, halogenated proteins, or a mixture of the aforementioned foaming agents, and - optionally at least one surfactant that is different from the foaming agent used in said solution; - at least one natural or synthetic foaming agent of animal or plant origin selected from the group comprising egg white, lecithins, and the natural or synthetic proteins, optionally hydrolyzed, such as serum proteins, in particular albumin, caseins, halogenated proteins, or a mixture of the aforementioned foaming agents, and - optionally at least one surfactant that is different from the foaming agent used in said solution; (iii) preparing a foamy mixture by mixing the aforementioned suspension obtained in step (i) and the aforementioned foam obtained in step (ii); (iv) stabilizing the foamy mixture obtained at the end of step (iii) to obtain said rigid foam, said foamy mixture being stabilized by heating to a temperature between 30°C and 200°C, by injecting CO 2, by adding dry matter powder or metal powder, or by adding weak acids, organic esters, alkylene carbonates or acetic esters.