Hi ck1990, welcome to Pearl-Guide!
What you have is commercial grade cultured Chinese freshwater pearls. Some of them have nice luster.
The good news is that these pearls are all nacre. They were cultured using a mantle-tissue implant placed into the freshwater mussel, but no bead was implanted, so they are nacre clear through. This means they are very durable-- you can wear them every day if you like.
The bad news is that you won't make any real money by selling them. The Chinese have greatly improved their culturing techniques in recent years, and now one can find almost-completely-round freshwater pearls that are highly lustrous, with clean surfaces and no rings. There just isn't much market for the lower grade pearls any more. But if you need to sell them anyway, you can look on eBay to see what similar pre-owned strands sell for (look at sold listings) or consign them locally.
Another idea, if you don't want to wear them as they are now, is to refashion the necklace. For example, you can create a casual look by interspersing pearls with inexpensive gemstone or Czech glass beads from your local beading store (or online sources.) Wander on over to the Lowly Beaders Club forum for some ideas.
