Giving a Diamond Its Color July 26, 2010
Posted by Jill Renee in : Jewelry , 4commentsHow Diamonds get Their Color
People should be forgiven for thinking that diamonds have no color and are brilliantly and sparklingly clear. The truth is that this sparkling, transparency is sold and marketed by diamond merchants and jewelers and the idea that a diamond should have any color at all has been banished from the minds of many. The truth is that almost every diamond has some color to some degree, and there can be a startling variety in the colors that are encountered in nature.
First of all, it is necessary to understand how a diamond is formed to be able to see how color variations are introduced by deformities in the otherwise, precise crystalline structure. Diamond is formed from pure carbon at great depths within the earth’s crust where the pressures and high temperatures are extreme. By heating and crushing the carbon atoms, they are forced into a compact atomic structure which is exceptionally strong and stable. So strong is this atomic, crystalline structure that diamond is the hardest, naturally occurring material known to man.
This crystalline structure is also colorless with light being able to pass through the atomic lattice unhindered. Pure diamond is indeed colorless, and there are some rare examples of them but expect to pay an exceptionally heavy price for them. The fact is that during the formation process, Mother Nature ensures that there is plenty of opportunity for variation in how the crystal structure is formed and which will affect color variation in different ways.
The bulk of color variation in diamonds is caused by impurities being present when the diamond is formed from the carbon melt.
The most common color for diamonds is yellow or brown, and most diamonds you are likely to encounter for jewelry purposes will not be completely colorless but will have a yellowish-hue. For most examples, there will be no discernible color or yellow-hue to be seen with the naked eye, however you may catch a tinge of yellow or a “dirtiness” to the tint of the stone. The yellowing is created by the presence of nitrogen in the carbon forming the diamond, and because this atom is of a slightly different size to the carbon atoms in the crystal lattice of the diamond, this causes some distortion. The physical distortion of the lattice-work in turn creates a distortion of the light passing through the stone, creating a yellow hue.
Other elements may be present such as hydrogen or boron (which will create a grey color), however it is not only impurities which create color variation.
Some diamonds are subjected to radiation sources when they are being formed or lying fully-formed in the earth’s crust. The effect of radiation on the crystal structure is to excite the atomic structure which in turn gives off energy in the form of light and this is responsible for green diamonds.
A third cause of color variation is known as “plastic deformation” and this involves a warping of the diamond crystal lattice itself. The precise arrangement of the carbon atoms is strained or in some instances, broken (but at the atomic level and not visible to the naked eye). Plastic deformation creates the red and pink colors found in diamonds and in some instances, brown diamonds are created by this defect.
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