I'm not an expert, but are you sure this isn't a labradorite? I've never seen an iridescent agate before. I just don't want you getting ripped off, because labradorite is more valuable than agate.
You too! I just wanted to mention it, because I know how lovely and in demand it is. It's gorgeous, and I'd be bidding if I didn't recently wipe my account out on a labradorite ring! Take care, and good luck to you and your bidders!