Jarosite minerals are of great importance to a range of mineral processing and research applications, as well as significant to the understanding of the environmental history of Mars and of theoretical interest as model compounds for spin frustration in Kagomé-Heisenberg antiferromagnetic materials. Traditionally, jarosites have been reported with rhombohedral symmetry, however we have synthesised jarosites with monoclinic symmetry and associated ordered iron-site deficiencies. This may have important implications for the magnetic properties of jarosites. The extent of the influence which H-bonding has on the behaviour of the structure is unclear. In this application we wish to investigate the H-Bond structure and thermal behaviour of these unusual jarosites over a range of 4.2 ¿ 700 K with a view to future magnetic studies.