This is a fragment with two sculpted surfaces, one rounded and one flat. The stone is black serpentinite with blue-green mottled coloration on surface.
From Nubia (Sudan), Kerma, K X corridor 11-2. 1914: Excavated by the Harvard University–Boston Museum of Fine Arts Expedition; assigned to the MFA in the division of finds by the government of Sudan.
Harvard University—Boston Museum of Fine Arts Expedition