Vtg white stone and gold large pendant or brooch

I believe the center stone of this pendant or brooch is actually stone but I am not completely positive. There is quite a bit of weight to this. The center stone is striated with a gray and yellowish green striation. The frame is a chain look with bottom scrolls. The back of the stone has 4/73 written in pencil on it. I don't know if that is a date or some other kind of indication for the piece. As a pendant - you could simply loop a chain through the top decorative loop at the top of the piece, or there is a hook on the back. As a brooch - there is a typical pin. Condition - excellent 2.25" x 1.75" Jewels4-16 checked