This invention relates to a hydrocarbon conversion process using a crystalline composition having a three-dimensional microporous structure of MA.sub.2 units where A is sulfur or selenium and having the empirical formula expressed in molar ratios: xR:MA.sub.2+0.2 :ZH.sub.2 O where R represents at least one organic templating agent present in the intracrystalline pore system, x is the moles of R, z is the moles of water and M is germanium or tin. This invention also relates to a composition having the empirical formula expressed in molar ratios: XR:M.sub.1-y M.sup.'y A.sub.2+0.2 :ZH.sub.2 O where M' is a metal such as cobalt, zinc, manganese, iron, nickel, cooper, cadmium and gallium.