Summary: Parahopeite, Zn₃(PO₄)₂.4H₂O , is the triclinic dimorph of hopeite. The crystal structure of parahopeite has been determined to be similar to phosphophyllite, Zn₂Fe(PO₄)₂.4H₂O and to hopeite in that one of the two zinc atoms is six-coordinated and the other is four-coordinated. Parahopeite differs from the other two minerals though because one of the P-O tetrahedral oxygen atoms is bonded to both the six- and the four-coordinated cations. That is, all four tetrahedral oxygen atoms are bonded to the four-coordinated zinc in parahopeite, whereas in phosphophyllite and hopeite only three of these oxygen atoms are so bonded. 1 Present address: Mining Faculty, Istanbul Technical University, Macka-Istanbul, Turkey.