This listing is for an Art Deco era marbled glass button. It has a faceted surface and looks slightly opalescent when the light moves across the surface - perhaps because the body of the glass is translucent white. It has been marbled with an olive green color which is unusual.
This button has a 4-way box shank and measures 1 1/16" in diameter.
Please see photos for details - contact me if you have any questions.