I believe it is a quahog pearl and one of the most interesting I have seen. Everyone who tries to sell them way overprice them. That ring has been on Kari's site for years, unsold. Others have joined the category since and they are way over priced. I put them all on my watch list. Some sold round on eBay a few months ago for $200-$400. The one that is left on eBay has been there for years and nary a bite at 7k or whatever they are asking.
Yours is not round and round seems to be the standard, but it is unique and gorgeous. I personally think it is more desirable than a round.