Improved slurry compositions comprising a mixture of a first type of particles and a second type of abrasive particles dispersed within an aqueous medium, and abrasive slurry compositions for use chemical mechanical planarization (CMP) processes, particularly abrasive slurry compositions for polishing of sapphire. These abrasive slurry compositions comprise a mixture of a first type of abrasive particles having a hardness that is harder than the surface being polished and a second type of abrasive particles have a hardness that is softer than the surface being polished, particularly mixtures of silicon carbide abrasive particles and silica abrasive particles, dispersed within an aqueous medium.