To reach a better understanding of the behavior of suspensions of charged colloidal platelets, takovite samples with a general formula Ni1-x, Al-x(OH)(2), An(x/z)(z-), yH(2)O, where An is an interlayer anion, were synthesized. These materials belong to the family of layered double hydroxides (also referred to as anionic clays). They can be easily prepared in the laboratory by coprecipitating mixed nickel and aluminum salts by NaOH. Their charge can be adjusted by changing the synthesis conditions, while the hydration properties can be modified by using various interlayer anions. On the basis of oscillatory measurements, rheological phase diagrams were obtained by plotting the sol-gel transition as a function of solid content and ionic strength for three monovalent anions: F-, Cl-, and NO3-. In all cases, the phase diagrams exhibit a negative slope, i.e., the sol-gel transition shifts toward lower solid contents for increasing ionic strength. The nature of the interlayer anion has a strong influence, the sol-gel line moving toward higher solid content in the order takovite F- < takovite Cl- < takovite NO3-. These differences cannot be assigned to changes in the surface charge of the samples as zeta potential measurements reveal a constant charge for the three anions. Postsynthesis hydrothermal treatments were then performed in order to modify the size and anisotropy of takovite NO3-. The aspect ratio of the particles appears as a key parameter controlling gel formation as it has a very pronounced effect on the rheological phase diagrams. Particles with higher aspect ratio exhibit a sol/gel transition at lower solid contents and with a reduced dependence on ionic strength.