Antimony triselenide is the chemical compound with the formula Sb2Se3. The material exists as the sulfosalt mineral antimonselite, which crystallizes in an orthorhombic space group. In this compound, antimony has a formal oxidation state +3 and selenium −2. The bonding in this compound has covalent character as evidenced by the black color and semiconducting properties of this and related materials. The low-frequency dielectric constant (ε0) has been measured to be 133 along the c axis of the crystal at room temperature, which is unusually large. Its band gap is 1.18 eV at room temperature.