I am no expert, but there have been a lot of posts on here like that, and it seems that no, they are not valuable. Still a very cool keepsake, though! I am wondering why it is that dark color. Anyone know?
It's just that it doesn't have the smooth surface and even color that would make it more sellable. A jeweler would have trouble selling a pearl that wasn't pretty. It definitely is cool and someone might give you some $ to collect it. Or keep it. A great story to tell your kids.