A dish like this would have been used in the preparation of cosmetics, specifically, for the grinding of pigments.  Malachite for green eye-shadow, galena for black kohl eye-liner, and perhaps ochre for blush, would have been placed in the dish in the form of small pieces of the material, and ground to fineness with a smooth stone.

Eye paint was not only an adornment, for men and women, but also seems to have had medicinal uses.  Malachite, an ore of copper, has mild anti-bacterial properties that might have helped ancient Egyptians ward off eye diseases.  The lead in kohl eye-liner would have had a similar effect, perhaps dissuading flies or other insects from laying their eggs.

The tilapia was an important source of protein, so common and important in ancient Egypt that it was represented in a hieroglyph, Gardiner's K1. The fish is mentioned in Spell 15 of the Book of the Dead, but its main importance symbolically, may have been that, as a mouth-breeding species, it mirrored the action of the creator god, who, in some versions of the creation story, spat out creation, and in another, spoke words which then took form.