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. The mineral tosudite also bears his name. It was approved as a valid species by the International Mineralogical Association in 1966.
Characteristics 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 between 2.5 and 3.5.
Classification Following the Nickel–Strunz classification, it is contained in the "09.EC.55" group:
+ Members of the 9.EC.55 group Mineral Formula Symmetry group Space group Baileychlore 1 or C1 or C Borocookeite (x ≤ 0,33) 2/m C2/m Chamosite 2/m C2/m Clinochlore 2/m C2/m Cookeite , 2 or 2/m C, C2 or Cc Donbassite 2/m C2/m Franklinfurnaceite 2 C2 Glagolevite 1 C1 Gonyerite unknown Nimite 2/m C2/m Odinite m Cm Orthochamosite unknown Pennantite 2/m C2/m Sudoite 2/m C2/m
Formation It has been first discovered in the Knollenberg Keuper formation, in the village of Plochingen, Stuttgart Region (Baden-Württemberg, Germany). 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
Use 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. The precise source of such formation of sudoite allowing to carve artifacts in rather large blocks remain unknown.
References
attribution translated from :fr:Sudoïte