The effects of shear rate and time on the seperation of fibres from the bundles of sepiolite from Eskisehir-Turkiye were studied. These sepiolite minerals are composed of large bundles of needle like fibres and this anisometry with the surface characteristics are responsible for their rheological behaviours. Rheological behaviour of sepiolite was studied using a suspension in water with a sepiolite:water weight ratio of 1:3. Shear to was varied between 300-2000 rpm and shear time up to 90 minutes. Viscosity values were taken after every 10 minutes for each shear rate. Transmission electron microscope was used for microstructural analysis. When sepiolite powders were mechanically dispersed in water, many of the single fibres were seperated from the bundles to form an entangled and randomly intermeshed network causing an increase in viscosity by entrapping water. Viscosity values were changed from 50 Ps to 500 Ps with,increasing shear rate up to up to 2000 rpm. Also, it was observed that the particle size and viscosity values were changed by mechanical mixing but the total surface charge did not change
