Vintage gold tone necklace w heart pendant and green emerald (?) insert

Bohemian delicate and feminine necklace. Good quality. In like new condition. 16" chain. 0.75" pendant (with bail). The green insert is securely prong set and looks like natural Columbian emerald, but I don't know for sure. There is a bit of a gold foil under the stone, which makes one think that it could be a rhinestone. But in the past, some real natural high end gemstones were prong set with a piece of real gold or silver foil underneath - to enhance their beauty.