Siegenite
| Siegenite | |
|---|---|
Siegenite from Buick mine, Bixby, Viburnum Trend District, Iron County, Missouri, USA | |
| General | |
| Category | Sulfide mineral Thiospinel group Spinel structural group |
| Formula | (Ni,Co)3S4 |
| IMA symbol | Seg |
| Strunz classification | 2.DA.05 |
| Crystal system | Cubic |
| Crystal class | m3m |
| Space group | Fd3m (#227) |
| Unit cell | a = 9.33 Å; V = 810.94Å3 |
| Identification | |
| Formula mass | 304.3 - 305 g/mol |
| Color | Light to steel-grey, violet-gray (tarnished) |
| Crystal habit | As octahedral crystals, granular, massive |
| Twinning | On {111}; polysynthetic |
| Cleavage | Imperfect on {001} |
| Fracture | Irregular to uneven, sub-conchoidal |
| Mohs scale hardness | 4.5 - 5.5 |
| Luster | Metallic |
| Streak | Grayish black |
| Diaphaneity | Opaque |
| Density | 4.5 - 4.8 g/cm3 (Measured) 4.83 g/cm3 (Calculated) |
| References | |
Siegenite (also called grimmite, or nickel cobalt sulfide) is a ternary transition metal dichalcogenide compound with the chemical formula (Ni,Co)3S4. It has been actively studied as a promising material system for electrodes in electrochemical energy applications due to its better conductivity, greater mechanical and thermal stability, and higher performance compared to metal oxides currently in use. Potential applications of this material system include supercapacitors, batteries, electrocatalysis, dye-sensitized solar cells, photocatalysis, glucose sensors, and microwave absorption.
In synthetic chemistry, a range of chemical compositions with the formula NixCo3−xS4 (0 < x < 3) are often referred to as the siegenite system. However, according to the new IMA list of minerals (updated November 2022), the normal spinel NiCo2S4 is called grimmite, the inverse spinel CoNi2S4 is called siegenite, and the endmembers Ni2+(Ni3+)2S4 and Co2+(Co3+)2S4 are called polydymite and linnaeite, respectively. In 2020, NiCo2S4 (grimmite) is approved as a valid mineral species by the IMA.