Mel D, welcome to the forum! That is an interesting earring! Is there a 2nd earring, or is it missing? If there is another, please take a photo of them together. And if possible size of earring, in height and length. I'm curious to see if the pearls are alike in shape.
If the pearls have a mother of pearl backing, and it's difficult for me to tell from the photo, they could be mabe (if cultured by man) or if found in the wild, blister pearls. Either type would be finished similarly, cut from the shell, filled carefully with resin and a mop backing applied. Can you see a line of separation between the top and the back?