Any fancy color green diamond is a rare treat to behold. Natural large green diamonds are almost unheard of. So attendees at Sotheby's November 17th auction in Geneva are in for a once in a lifetime glimpse. Up for bidding will be a 2.52 carat cushion shaped natural green diamond so rare no one can calculate what the market will bring for this beauty. Pre-auction estimates call for a price range between $3.1 to $5.1 million dollars.
No one completely understands the mechanism behind a natural green diamonds' coloration. But it is believed to involve that crystals' close proximity to subterranean natural irradiation. Diamonds undergoing laboratory treatment mimicking this natural occurrence can also produce green diamonds. Their coloring is often different, perhaps having a yellowish back color to the green hue. Nevertheless diamonds such as this important jewel have a rock solid provenance verifying its origin as natural.
Often on green crystals rough exterior, or skin, there appears to be a concentration of color. This trait requires cutters to be expert in polishing these rarities so as not to remove a concentration of color in the polishing process.
The most famous large natural green diamond is the celebrated Dresden Green Diamond residing at a museum in Dresden Germany. That 41 carat egg shaped beauty is confirmed to be at least 250 years old so it is also natural as laboratory irradiation treatment is a modern invention. But you knew that.