Citation: Bell, Anthony M. T.; Henderson, C. Michael B. (2018). Crystal structures of K~2~[XSi~5~O~12~] (X = Fe^2+^, Co, Zn) and Rb~2~[XSi~5~O~12~] (X = Mn) leucites: comparison of monoclinic P2~1~/c and Ia{\/overline 3}d polymorph structures and inverse relationship between tetrahedral cation (T = Si and X)---O bond distances and intertetrahedral T---O---T angles. Acta Crystallographica Section B, 74, pp. -.