A cork-like type of flooring material which is light brown and porous. Magnesite flooring was commonly used as a finishing surface on concrete floor slabs mainly during the 1960s and 70s to make the concrete level and provide insulation. It is composed of calcined magnesite, magnesium chloride, sawdust, ground quartz or silica, and fine powdered wood waste. However, it is associated with water damage because it is very porous and readily absorbs water. It lets water through to the concrete below easily and this can lead to concrete spalling (or concrete cancer, see above). It also retains the water unless regularly exposed to sunlight for evaporation. This means it can rot away and become soggy in damp patches.