Diamonds are typically known to be colorless or 'white', but the most common colors are yellow and brown. Golden and brownish hues are owed to traces of nitrogen impurities. Brown and yellow diamonds are often referred to as 'champagne' or 'cognac' diamonds. Other diamond colors include pink, red, orange, blue, green, gray and black. Blue diamonds are colored by boron impurities, while other fancy colors are the result of irradiation and in some cases, crystal lattice defects. The official color grading system for colorless to low-saturation yellow and brown diamonds ranges in scale from 'D' (completely colorless) to 'Z' (light-yellow). Fancy colors are graded on an entirely different scale.
Diamond Clarity and Luster
Diamonds exhibit a strong sub-metallic adamantine luster. Though diamonds can be transparent to opaque, only transparent stones are faceted. Most diamonds are too heavily flawed to be considered valuable, in fact, only roughly 20% of all diamond deposits are of any gemstone value. Of the 20% yield, the vast majority will still contain flaws and inclusions even if they are minute. A flawless diamond is exceptionally rare.Diamond clarity is graded on a scale that factors both size and visibility of flaws and inclusions, ranging from 'FL' (Flawless) to 'I3' (large inclusions visible to the naked eye). Although the diamond clarity grading scale is considered official, an assigned clarity grade for any single specimen can vary tremendously depending on who did the evaluation or where the stone was evaluated. It is not uncommon for a single stone to be given two different clarity grades by two different labs - the same applies for cut and color grading of white diamonds.