| Sudoite | |
|---|---|
| General | |
| Category | Chlorite_group |
| Formula (repeating unit) | Mg2Al3(Si3Al)O10)(OH)8 |
| Crystal system | Monoclinic |
| Identification | |
| Color | White to light green |
| Mohs scale hardness | 2.5–3.5 |
| Luster | pearly, dull |
| Refractive index | nα = 1.581 à 1.583 nβ = 1.584 à 1.589 nγ = 1.591 à 1.601 |
| Birefringence | biaxial (-) ; δ = 0.010 to 0.018 2V = 64 to 70° (measured) 2V = 68 to 72° (calculated) |
| References | .[1][2] |
Sudoite is a mineral from the chlorite group. It was named after Toshio Sudo (1911-2000), professor of mineralogy at the University of Tokyo, in Japan, and a pioneer of clay science.[3] The mineral tosudite also wears his name. It was approved as a valid species by the International Mineralogical Association in 1966.
Sudoite is a clay mineral with chemical formula defined as Mg2Al3(Si3Al)O10)(OH)8. it has a monoclinic crystal system. Its hardness on the Mohs scale is comprised between 2.5 and 3.5.
Following the Nickel–Strunz classification, it is contained in the "09.EC.55" group:
| Mineral | Formula | Symmetry group | Space group |
|---|---|---|---|
| Baileychlore | (Zn,Al) 3[Fe 2Al][Si 3AlO 10](OH) 8 |
1 or 1 | C1 or C1 |
| Borocookeite | Li 1+3xAl 4-x(BSi 3)O 10(OH,F) 8 (x ≤ 0,33) |
2/m | C2/m |
| Chamosite | (Fe,Mg,Fe) 5Al(Si 3Al)O 10(OH,O) 8 |
2/m | C2/m |
| Clinochlore | (Mg,Fe) 5Al(Si 3Al)O 10(OH) 8 |
2/m | C2/m |
| Cookeite | LiAl 4(Si 3Al)O 10(OH) 8 |
1, 2 or 2/m | C1, C2 or Cc |
| Donbassite | Al 2[Al 2,33][Si 3AlO 10](OH) 8 |
2/m | C2/m |
| Franklinfurnaceite | Ca(Fe,Al)Mn 4Zn 2Si 2O 10(OH) 8 |
2 | C2 |
| Glagolevite | NaMg 6[Si 3AlO 10](OH,O) 8·H 2O |
1 | C1 |
| Gonyerite | Mn 3[Mn 3Fe][(Si,Fe) 4O 10](OH,O) 8 |
unknown | |
| Nimite | (Ni,Mg,Fe) 5Al(Si 3Al)O 10(OH) 8 |
2/m | C2/m |
| Odinite | (Fe,Mg,Al,Fe,Ti,Mn) 2,5(Si,Al) 2O 5(OH) 4 |
m | Cm |
| Orthochamosite | (Fe,Mg,Fe) 5Al(Si 3Al)O 10(OH,O) 8 |
unknown | |
| Pennantite | Mn 5Al(Si 3Al)O 10(OH) 8 |
2/m | C2/m |
| Sudoite | Mg 2(Al,Fe) 3Si 3AlO 10(OH) 8 |
2/m | C2/m |
It has been first discovered in the Knollenberg Keuper formation, in the village of Plochingen, Stuttgart Region (Baden-Württemberg, Germany).[4] Despite being an unlikely mineral, it has been described in every continent but Antarctica and Oceania. It is found mainly in hydrothermal or high-pressure/low-temperature (HP/LT) metamorphism contexts[5][6][7]
This mineral has been used as gemstone for the production of personal ornaments, beads and pendants, during the Early Ceramic Age (500 BC – 500 AD), in the Lesser Antilles.[8] The precise source of such formation of sudoite allowing to carve artifacts in rather large blocks remain unknown.