This a palette.
It is from Upper Egypt. Eye makeup did not come ready-made. The pigments used for kohl had to be ground to powder using a greywacke or ‘slate’ palette like this. Diamond-shaped (rhomboid) palettes were most common, but the palette could be a fancier shape such as a fish or, like this one, a turtle. This one shows little if any sign of use. This a palette. It is carved from slate. It is at least 5,100 years old, dating to the Pre-dynastic Period (about 5500-3100 BCE).