Joey,
Welcome! Ash got it right, I think, Chinese freshwater pearls, nugget shape. What's great about them is they are tissue nucleated, with just a tiny piece of donor tissue, and as such are all nacre. I love the coin clasp, haven't seen that before, you probably can wear it in front too, for a more casual look. The multi strand necklace is right in style now. (Not certain it was ever out of style!)