I've been drooling over emerald for quite awhile now. But having the money for this is sheer fantasy!
There is a Summer necklace that is designed to heighten the effects of a small amount of emerald. It is really only about 5 carots emerald, but has the effects of about 16-20 carots, I don't remember specifically.
The website has the prices. I often will just call the Gemisphere number and ask them the current pricing.