Seeligerite

Seeligerite is a rare complex lead chloride iodate mineral with formula: Pb₃Cl₃(IO₃)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_α=2.120 n_β=2.320 n_γ=2.320.^[2]

Seeligerite
Seeligerite crystals, from Sierra Gorda, Antofagasta Region, Chile.
General
Category	Iodate minerals
Formula	Pb3Cl3(IO3)O
IMA symbol	Sli[1]
Strunz classification	4.KB.15
Crystal system	Orthorhombic
Crystal class	Disphenoidal (222) H-M symbol: (2 2 2)
Space group	C2221
Identification
References	[2][3]

It was first reported in 1971 from the Casucha Mine, Sierra Gorda, Antofagasta Region, Chile.^[2]