Genuine sea glass are pieces of glass that have been in the ocean for quite a while. They have been polished by water and sand so they have a wonderfully matte/soft surface with nearly all edges being smooth.
These days, a lot of so-called 'sea glass' is just normal glass, treated to a matte finish. I have some of those pieces in stock, but I always point out that those are man-made pieces, not ocean made.
This necklace is made with a piece of genuine, ocean-made sea glass, found at Scarborough Beach, in Perth/Australia.