On the structural relations of malachite. I. The rosasite and ludwigite structure families

摘要: The crystal structures of malachite Cu2(OH)2CO3 and rosasite (Cu,Zn)2(OH)2CO3, though not isotypic, are closely related. A previously proposed approach explaining this relation via a common hypothetical parent structure is elaborated upon on the basis group–subgroup considerations, leading to conclusion that aristotype should crystallize in space group Pbam (No. 55). An ICSD database search for actual representatives leads interesting observation type ludwigite (Mg,Fe)2FeO2BO3, which adopted by several natural synthetic oxide orthoborates M3O2BO3, related malachite–rosasite thus family hydroxide carbonates M2(OH)2CO3 general. Relations within both families their analogies summarized joint simplified Barnighausen tree.