You know, if it weren't for Vilya and Narya, I'd be convinced Tolkien didn't know gems came in anything other than white and green...
You're forgetting hobbit names.
And the Man in the Moon.
I'd kind of agree if you mentioned grey and green for eye-colour, though.
...
The only seriously ancient things beginning with O I can think of are ...
ORMAL (but did any jewels get sucked into it and burned?)
OIOLOSSE (but that word/name is Quenya
OROME (but is he into bling?)
There's Osse, but see parenthesis after Orome.