What is FIRESLATE? Consisting solely of Portland cement, silica sand, water, and fillers, formed under 400 tons of pressure, steam- and air-cured, FIRESLATE is a man-made material. Like slate and other natural stone, FIRESLATE is dark, rich, and has a solid depth of character. But unlike slate and other natural stone, it has no veins or strata to delaminate. It handles heat and weighs 40 percent less than natural stone. Even with its natural ingredients and stone-like beauty, FIRESLATE costs less than the plastic design materials on the market.