Formation of racemic pentose-2,4-bisphosphates is demonstrated, starting from glycolaldehyde phosphate and glyceraldehyde-2-phosphate, and induced by mixed valence double layer metal hydroxide minerals. The reactions proceed from dil. aq. reactant solns. (1.5 mM) at near neutral pH. Conditions have been established, where ribose-2,4-bisphosphate is the major product (.apprx. 48%) among the pentose-2,4-bisphosphates, which are formed with up to 25% yield. [on SciFinder (R)]