Comparisons in shear behaviour are made between aqueous suspensions of a laterite ore and aqueous suspensions of pure goethite ($alpha$-FeOOH), following prior papers in which the rheologies of the two mineral suspensions were characterized individually. Drawing comparisons is appropriate because the ore sample was about 65% goethite and it was originally thought that the pure goethite might serve as a model of the more complex laterite. Viscosity measurements of the two suspensions show that, at the same solids fraction, the goethite suspensions were more viscous by an order of magnitude, even though the goethite particles had much smaller aspect ratios. Similarly, yield stresses for the goethite suspensions were at least an order of magnitude higher. The most significant difference was in transient behaviour. Time-dependent effects were investigated by subjecting a fluid to a step change or a ramp sequence in shear rate, and measuring the resulting shear stress over time. In most cases, transient behaviour could not be detected in the goethite suspensions, whereas stresses in the laterite suspensions relaxed over periods of order 10 seconds. The disparate results indicate that a goethite suspension is a poor model of a laterite slurry.