<<I bought a diamond ring last year, ... definitely NOT described ... is there anything I can do? Or is it too late?>>
Hello 'litollamb',
Yes, it is too late. You will already be well acquainted with the ebay policy on items which are
not as described:
http://pages.ebay.ca/help/buy/item-not-received.html
When you buy something like that, the time to take it to the jeweller is before your 45 day deadline
for restitution has passed.
You say you paid with paypal, so as you can see from the link, after 45 days ebay/paypal will do
nothing to help you.
In future, if you are going to buy what you expect will be 'real' jewelry (as opposed to that cheap
costume junk you only want to wear once or twice), -- get it looked at the moment it arrives.
At this point all you can do is have the piece repaired, -- and accept that if you did not notice the flaw
in all this time, no one else (other than a jeweller) will. It just does not have the value you anticipated.