The magnetic properties of two types of material derived from the brucite lattice, M(OH)2 are described. The structure-directing effects of simple templates on the brucite lattice parallels the processes seen in nature in the formation of biominerals. The first type exemplified by Fe17/Fe19 aggregates models the structural features of the iron storage protein ferritin. The magnetic behaviour also reveals some interesting parallels with the magnetic phenomena reported previously on ferritins. We have used a combination of experimental techniques including DC, AC and RF susceptibility measurements on powders and a microSQUID on single crystals. The second type is based on an extended-defect brucite structure with stoichiometry M2(OH)2 (ox) for M = Fe2+, Co2+. They show long-range ordering to antiferromagnetic phases and then, at much lower temperatures, undergo a phase transition to canted antiferromagnetic states. Symmetry arguments are used to predict the spin configurations in these extended materials.