A good looking FAKE inkstone! It is a copy of a historical stone but is made of unfired clay. If used makes a slippery surface that will not make ink unless one uses an ink made with a water soluble glue which then produces a slurry of ink and clay.
Inkstone is one of the importance tool among the "four treasures of study" for Chinese calligraphy.
PALE CELADON JADE BRUSH WASHER QING DYNASTY, 18TH CENTURY of circular form, with countersunk base and rounded sides incurved at the rim, the interior crisply carved in relief with a single spray of poppy flowers issuing the characteristically jagged leaves and two delicately petalled blooms, the stone softly mottled with a pale russet inclusions Diameter 5 1/4 in., 13.2 cm. | Sotheby's