It is not recommended to use United Statess Ranchers Blend Schist for exterior applications in very dusty climates. Schist is a type of metamorphic rock that can be quite porous, meaning it can absorb moisture and particles from the air. In a dusty environment, the particles can easily get trapped in the pores of the stone and cause staining or discoloration over time. Additionally, the constant exposure to dust and other airborne particles can also accelerate the weathering process of the stone, causing it to deteriorate more quickly. Therefore, it is advisable to choose a more suitable material for exterior applications in very dusty climates.