Yes, that's how mabe' pearls are made. A shape, in this case a teardrop, is put on the inside of a mollusk along with some mantle tissue. The pearl nacre grows over the shape. When the pearl is harvested, the pearl is cut out of the shell and the shape is removed leaving a dome of pearl nacre that is filled with resin. Then a mother of pearl backing is glued on to seal the back. They give a big pearl look with lighter weight than if it were solid shell or nacre.
Sorry, they're not worth much. My sister and I inherited several pairs of 1990's era mabe' pearl earrings from our mom, and they're not our style. We can't even give them away. Even the pawn shops in my area won't buy them because they can't resell them. They're not vintage enough, yet. I looked on Ebay, and mabe' pearl earrings with no gemstones are in the asking range of $20 to $200. Earrings with lots of gold and gemstones had much higher asking prices. Doesn't mean the sellers are getting those prices though.
If you like them, give them a gentle wash to remove grime. Don't use a jewelry dip. Don't use a steamer. Just a little soap and water and dry them with a soft towel. Then enjoy wearing them. Yours have a very unusual swirl design that's very cool looking. I wear my mom's teardrop shaped ones occasionally.
