I am sure that they are. You can see the diamond stamp beside the 14k, and the ring was my mother's who owns only fine, real jewelry (she just doesn't like gold anymore). However, I haven't had it professionally appraised so I have no supporting documentation and I will refund if the winner isn't satisfied with the ring.
Do you still have the receipt for this? Because without it insurance will not do any good. I know this from first hand experience. And also happened to talk to the post office about it today. It doesn't matter if you buy insurance or not, if you don't have the receipt, they won't give you anything. The safest way to send anything is by having the person sign to get it.
I would talk to Canada Post - I haven't had a receipt for any of my claims, and everything went smoothly. They just asked what I was shipping and the value. It was eBay stuff to Europe, but they never asked for the auction number *shrugs*
Call them - the local ones at the post offices don't deal with claims anyways, and will give you a different answer every time.