Seeligerite is a rare complex lead chloride iodate mineral with formula: Pb<sub>3</sub>Cl<sub>3</sub>(IO<sub>3</sub>)O. It is a yellow mineral crystallizing in the orthorhombic system. It has perfect to good cleavage in two directions and a quite high specific gravity of 6.83 due to the lead content. It is translucent to transparent with refractive indices of n<sub>ñ</sub>=2.120 n<sub>ò</sub>=2.320 n<sub>ó</sub>=2.320.
It was first reported in 1971 from the Casucha Mine, Sierra Gorda, Antofagasta Region, Chile.