sumi

inkstick

The regular black inksticks are made of ground charcoal. Sumi are ground on the suzuri (inkstone) with water to make ink for use in calligraphy. Along with suzuri, fude (brush), and kami (paper), it is one of the Four Companions of the Writing Chamber.

Symbols of Japan: Thematic Motifs in Art and Design
Merrily Baird