MYSTERY FACE.  I've spent the last hour and a half looking at literally thousands of stone faces and/or masks of every period and every continent- NOTHING even vaguely like this was out there.  It's a hard and heavy stone--very dense. appx 6 x 4 inches about 3/4 inch thick.  Had been highly  polished at one time and much of the surface is undisturbed.  Very tiny crystals or mica chips scattered irregularly throughout. Because of it size and thickness and flat back I can't imagine it is a mask. . I thought Africa--no help.  I thought Polynesian--  no help. Best guess is that it was a ceremonial (because it's so heavy) pendant given the huge hole in the "forehead".It's not something anyone would wear around just for the look--too big and mainly too heavy.