Diamond & Estate Trust couldn’t let our colored diamond week end without spotlighting the brown diamond, which has quickly become a luxury jewelry staple over the past few years. With celebrities such as Cate Blanchett, Hillary Swank, Lea Michelle, Cameron Diaz and Jennifer Lopez trusting the cognac diamond to complete their Red Carpet looks, you’ll be in fashionable company once you select a gorgeous brown diamond for your own collection. Here’s a quick guide to the brown diamond, also known as the cognac diamond or the chocolate diamond. A orange-brown diamond from the Diamond & Estate Trust collection. How rare are brown diamonds? Only one in 10,000 diamonds mined is a color other than white, making any colored diamond a rarity. Within the spectrum of colored diamonds , the brown diamond is in the middle of the road: a little more common than the yellow diamond , blue diamond , pink diamond , green diamond , and red diamond. But even though the brown or cognac diamond isn’t the rarest of the colored diamonds , it is still exceptional to find one naturally. Most of the world’s exquisite brown diamonds are produced at Australia’s Argyle Mine (which is also famous for champagne diamonds and pink diamonds). How do brown diamonds get their color? Because brown diamonds have soared in popularity lately, gemologists are devoting more time to understanding just what gives the brown diamond its beautiful, rich cognac color. Like most colored diamonds, a brown diamond gets its hue because of a structural irregularity in the diamond’s lattice. Some varieties of brown diamonds include golden brown diamonds,  brownish orange diamonds, champagne diamonds and cognac diamonds. As with any other colored diamond , the most important word to look for in its color classification is “natural.” Diamonds treated with irradiation or other artificial methods to achieve a brown color are far less valuable and far more common than natural fancy brown diamonds. What are some famous brown diamonds?