The vast majority of all diamonds contain some nitrogen. In most yellow diamonds the nitrogen atoms have grouped themselves in very specific ways. This happens during and right after the diamond is formed. These nitrogen arrangements absorb light in the blue region of the spectrum producing a yellow color. Yellow diamonds can contain an orange, green or brown modifying color.
The most notably large and intense yellow diamonds have been discovered primarily in South Africa. The Allnatt, a 101ct cushion shape fancy vivid yellow diamond is perhaps the most significant yellow diamond in history, named after its original owner, Major Allnatt, in the 1950s. One of the largest polished diamonds in the world is the Incomparable, a 407 carat internally flawless brownish yellow diamond. Yellow diamonds account for about 70% of natural color diamonds graded by GIA each year