gosu porcelain
Refers to a type of porcelain that uses gosu (cobalt pigment) for underglaze blue decoration.
This plate is decorated with gosu.
asbolite; zaffer
Technical terms for the raw cobalt mineral used as a pigment, especially in ceramics. Asbolite is an earthy cobalt oxide; zaffer is an impure cobalt oxide used historically.
Gosu is made from a mineral containing cobalt.
The term 呉須 (gosu) likely derives from the Chinese word for cobalt pigment used in porcelain. The exact historical derivation is uncertain.