Wear properties of the rocks should be considered in any type of rock machineability investigation since they affect tool cutting performance dramatically. Rates of tool wear are very dependent on structure, composition, and properties of the excavated material. High-strength rocks give rise to high stress on the cutting edge, cracks are formed, and tool life is then reduced. Quartz has a great influence on the wear process, which in turn controls the economic success of rock machinery. Tool materials, design and operational variables, strength of the rock, shape, and content of quartz affect the life of cutting tools and makes the problem very complex indeed. Hence, this chapter should be considered in the light of such complexity.