The Merlin Diamond Mine in Australia's Northern Territory has yielded not one — but five — ultra-rare green diamonds, the largest of which weighs 1.42 carats. The discoveries are noteworthy because barely a handful of green diamonds are introduced to the market each year and the finest-quality ones can fetch upwards of $3 million per carat.

Mining company Merlin Diamonds Ltd. announced that the five diamonds — some described as intense green — were all discovered at the Kaye Pit, about 80km south of Borroloola near the Gulf of Carpentaria. Additional green gems were also pulled from the mine and were being validated as diamonds by independent gemological experts, according to the company.

The green diamond revelations are the latest in a string of good news for the mining operation. Merlin, which was already known for its high-quality, large, super-white gems, discovered a rare blue diamond in December and a 35.26-carat brown diamond in January. Australia's largest diamond, a 104.73-carat stone, also originated at the Merlin Diamond Mine, which was purchased from Rio Tinto in 2004.

When it comes to fancy-colored diamonds, the two rarest colors are red and green. Green diamonds owe their color to the natural radiation present during their formation inside the earth. Green diamonds can range from light mint green to vivid grass green. The value increases with the intensity of the color.

An excellent example of a fancy vivid green diamond is the 5.03-carat "Aurora Green," which sold for $16.82 million at Christie's Hong Kong in May of 2016. It is the most expensive green diamond ever sold at auction and the largest natural fancy, vivid green diamond known to exist.

Credits: Rough diamond image courtesy of Merlin Diamonds Ltd.; Map by Googlemaps; Aurora Green image courtesy of Christie’s.