Microporous crystallized gallium phosphate and its substituted derivatives, characterized by:a) the following approximate general formula:R.sub.r Ga.sub.g P.sub.p X.sub.x O.sub.2 F.sub.f hH.sub.2 O where the sum of g, p and x is equal to 1, and whereg is a number from 0.3 to 0.5,p is a number from 0.3 to 0.52,x is a number from 0 to 0.4,r is a number from 0.01 to 0.2,f is a number from 0.01 to 0.2,h varies according to the degree of hydration of the solid, from 0 to 0.5.R is an organic compound selected from the group formed by cyclic amines,X is a heteroatom selected from the group formed by the elements: Li, Be, Co, Mg, Mn, Zn, Al, B, Cr, Fe, Ge, Si, Ti, As and Vb) an X-ray diffraction diagram shown in Table 1 of the description,and a method of preparing them.