amassette

from The Century Dictionary.

• noun An instrument, usually of horn, like a palette-knife or spatula, with which in the preparation of pigments the colors used in painting are collected and scraped together on the stone during the process of grinding them with the muller. Also written amazette.

from the GNU version of the Collaborative International Dictionary of English.

• noun An instrument of horn used for collecting painters' colors on the stone in the process of grinding.