Calcium silicide (CaSi2), also called calcium disilicide, a ferroalloy containing 23–32 percent Ca and 2–4 percent Fe (the remainder is Si), is an inorganic compound, a silicide of calcium. It is a whitish or dark grey to black solid matter with melting point between 700-935°C. It is insoluble in water, but may decompose when subjected to moisture, evolving hydrogen and producing calcium hydroxide. It decomposes in hot water. It is flammable and may ignite spontaneously in air.