Because slate is stable thermally and chemically inert; many laboratory tables are topped with slate. Which renders those pretty hard to move, too, but they supply a rut for chemists and others who work with volatile chemicals to purpose. It wouldn't do to accidentally drop hydrochloric acid on a wooden table top, however if it happened on a slate one it wouldn't matter.
Most concrete stone will hold up fine outside in every weather assuning that it is fashioned and relating to that purpose. Concrete needs microscopic air pockets so the moisture can expand and contract without affecting the solid concrete sections. Our proprietary mix formula, as do other exterior concrete ledge Stone for textured Surfaces includes air-entrainment agents in order to assist prevent the product from conking out under freeze-thaw conditions like those found in northern environments. Formulas can be adjusted for extreme conditions and special applications as well by adding extra air-entrainment agent.