You could search a long time before you'd find glass hearts as beautiful as these.
In fact, I did search for quite some time before I found these handmade hearts in various designs and colors.
This heart has a dramatic but sweet design of flowers, swirls, and little raised balls of glass. One is the center to a flower, the others are part of the overall design.
The heart is about 19 mm in size and each one is handmade individually in California of Italian and German glass by a company called Grace Lampwork.
I used sterling silver wire to attach the heart to a jump ring with a wrapped loop. Then I threaded black velvet ribbon through the ring, and added a high quality cultured pearl on another jump ring.
You can't see the pearl in this photo, but here's a different necklace with a pearl: Glass Hearts: a Variation
I have some earrings made with the same pearls and jump rings: Precious Pearl Earrings
The black velvet ribbon is long enough to tie in a bow at the back of your neck. You should be able to adjust the length to suit the neckline you are wearing it with.
If the ribbon seems too long, just cut the ends with very sharp scissors. It won't fray as long as the scissors are sharp.
Price: $85, which includes postage, insurance, and taxes. Buy this necklace: