"The Argyle deposit is shaped a little like a human molar, with a wide top and bottom that descends in a forked shape. On geological cutaway maps, these forks look like the roots of a tooth. This pipe is loaded with diamonds that probably emerged from the earth’s mantle around 1.6 billion years ago. But unlike almost every other diamond lode on earth, it is not made of kimberlite. It is a volcanic rock named lamproite, which is a close cousin to kimberlite. There was a large concentration of nitrogen in this lamproite that turned all the diamonds a yellowish color and gave a few of them a weird punkish cast."