The hydroxy interlayer is comprised of Al–OH^–,H₂O complexes (also possibly with Fe³⁺ or Mg2+) and is located in the space (or interlayer) between the 2:1 layers of phyllosilicates. The cations are octahedrally coordinated by the H₂O and OH^–. The hydroxy-interlayer does not form continuous sheets and additional H₂O may occur above and below the Al–OH^–, H₂O complexes. See hydroxy-interlayered mineral.
Cf., hydroxy interlayering, hydroxy-interlayered smectite, hydroxy-interlayered vermiculite