Glass mosaic inlay
Not on view
Translucent purple and streaky pale green; opaque white and grey-blue.
Square, with slight convex upper surface; ground, straight edges.
Central ground in green, outlined with an irregular wavy pattern in white and blue, and a purple ground at corners.
One corner missing, and another chip in one side; many pinprick bubbles; polished upper surface, with some pitting of surface bubbles; some pitting, dulling, and soil encrustation on bottom surface.
Probably not ancient.