Isomorphism
The property of two or more different substances crystallising in the same structural form.
Unit
Dimensionless
In depth
Isomorphous substances have analogous formulae and ions of similar size and charge, so they can form continuous solid solutions and grow mixed crystals in any proportion. Mitscherlich's discovery of isomorphism gave nineteenth-century chemists a way to determine atomic weights.
Examples in the real world
The alums KAl(SO₄)₂·12H₂O and KCr(SO₄)₂·12H₂O; NaNO₃ and CaCO₃, which share the calcite structure.