Sudoite

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 wears his name. It was approved as a valid species by the International Mineralogical Association in 1966.

Caracteristics
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.

Classification
Following the Nickel–Strunz classification, it is contained in the "09.EC.55" group:

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.