(Hemihedral).
Here there are three dyad axes, but no planes of symmetry and no
centre of symmetry. The general form {hkl} is a bisphenoid (fig. 61)
bounded by four scalene triangles. The other simple forms are
geometrically the same as in the holosymmetric class.
Examples: epsomite (Epsom salts, MgSO4.7H2O), goslarite (ZnSO4.7H2O),
silver nitrate, sodium potassium dextro-tartrate (seignette salt,
NaKC4H4O6.4H2O), potassium antimonyl dextro-tartrate (tartar-emetic,
K(SbO)C4H4O6), and asparagine (C4H8N2O8.H2O).