A low-gloss kohiki (粉引) glaze with faded rust-orange specks. Kohiki is a glaze technique originating from Korea characterised by a fine white powdery slip. This style has had a close association with tea since the 1500.
This bowl also has a pronounced chadamari* (茶だまり).
*Chadamari is a dip or area at the bottom of the chawan that allows any leftover matcha to pool. This is one aspect of (visual) appreciation during tea ceremony.