A process for producing solid vermiculite products which are stable in water which comprises incorporating a source of ammonia or ammonium ions or a basic substance, preferably urea, in an aqueous suspension of vermiculite lamellae, shaping the suspension and removing water from the suspension by heating the shaped suspension at a temperature above 100.degree. C., preferably above 150.degree. C., such that ammonia or a basic substance is liberated within the suspension. The invention includes an aqueous suspension of vermiculite lamellae containing a source of ammonia or ammonium ions or a basic substance and a dry-powder mixture of vermiculite lamellae and a source of ammonia or ammonium ions or a basic substance.