Cadmoindite

Cadmoindite
Cadmoindite, from Kudriavy Volcano, Far Eastern Region, Russian Federation
General
Category	Sulfide mineral Thiospinel group Spinel structural group
Formula (repeating unit)	CdIn2S4
Strunz classification	02.DA.05
Crystal system	Cubic
Space group	Isometric hexoctahedral H-M symbol (4/m 3 2/m) space group Fd3m
Unit cell	a = 10.81 Å; Z = 8
Identification
Formula mass	470.32 g
Color	Black to dark brown
Crystal habit	Microscopic octahedral crystals
Fracture	Conchoidal
Luster	Adamantine
Diaphaneity	translucent
Optical properties	Isotropic
References	[1] [2]

Cadmoindite (CdIn₂S₄) is a rare cadmium indium sulfide mineral discovered in Siberia around the vent of a high-temperature (450–600 °C) fumarole at the Kudriavy volcano, Iturup Island in the Kuril Islands. It has also been reported from the Kateřina Coal Mine in Bohemia, Czech Republic.^[2]

Crystal Structure

CdIn₂S₄ exhibits the spinel structure, which can be described by a cubic unit cell with 8 tetrahedrally coordinated and 16 tetrahedrally coordinated cation sites. The distribution of Cd(II) and In(III) over the cation sites is difficult to elucidate from standard X-Ray Diffraction techniques because the two species are isoelectronic, but both Raman spectroscopy measurements on synthetic samples^[3] and density functional theory simulations^[4] indicate that about 20% of the tetrahedral sites are occupied by In(III) cations.

References

1. Cadmoindite Webmineral Data
2. Cadmoindite mineral information from Mindat.org
3. Ursaki, V. V.; Manjon, F. J.; Tiginyanu, I. M.; Tezlevan, V. E. (2002). "Raman scattering study of pressure-induced phase transitions in MIn₂S₄ spinels". J. Phys.: Condens. Matter. 14: 6801. doi:10.1088/0953-8984/14/27/304.
4. Seminovski, Y.; Palacios, P.; Wahnon, P. M.; Grau-Crespo, R. (2012). "Band gap control via tuning of inversion degree in CdIn₂S₄ spinel". Applied Physics Letters. 100: 102112. doi:10.1063/1.3692780.