Colored diamonds are rarities among the most brilliant and usually expensive of all gemstones, but green diamonds are even more rare; different natural phenomena combined to give this diamonds the shade to stand out among the others, and has become a recent interest in gemmology fields.
Diamonds with a green hue are found in Brazil and Zimbabwe and are defined by the type of process for their formation.
A recent article published by the Gemological Institute of America on their Gems and Gemology quarterly publication details everything there is to know about the rarest of diamonds, and makes for an interesting short read. Check out the PDF for the article!