While some green diamonds have a trace amount of nickel mixed into their carbon, the coloration in most green diamonds is due to the natural radiation from nearby rocks, which traps electrons to create a green surface colour. This minute amount if trace radiation does not always affect the entire gem, meaning that the stone may be green only in patches or on the surface. In these gems, the coloured surface portion is the external layer and some of the natural green can be lost during polishing.
If the colour is not lost during the polishing stage, the diamond is awarded a natural green colour grade. It can be said that this is the reason that green diamonds are so rare, as mostly the green colour is only skin deep.
All green diamonds have at least some small patches of ?skin? left on the stone also known as natural inclusions. It is very easy to replicate green colouration artificially, so the natural inclusions assist the diamond graders in determining the origin of the colour. Awarding a green diamond a natural colour origin is one of the hardest tasks a diamond grader can face contributing to the value and rarity of these diamonds.
Natural green diamonds come in an array of colours from khaki and olive green to the rarest turquoise colours, emerald and peacock green.
The value of natural green diamonds is based on rarity and not so much on beauty, though they are certainly beautiful, making pure greens very highly valued. Green diamonds can also have a combination of colour shared with blue (as a secondary colour ie: bluish green) are even rarer and more highly prized than straight green coloured diamonds.
Natural green diamonds continue to appreciate in value and set world record diamond prices. Natural green stones in the intense and vivid colour intensity ranges that are above 0.75ct in weight are priced in the hundreds of thousands of dollars per carat.
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