Diamond transparency

Transparency can play a major role in determining the value and desirability of a diamond. In most cases, the higher the transparency the more valuable the diamond.

Polished gemstones, including diamonds, range from transparent to opaque, depending on how much you can see through the material. There are three main categories of transparency:

Transparent – Materials you can see through. Objects or writing, for example, placed behind them can be viewed clearly and distinctly. Most gem-quality rough and cut diamonds would be defined as transparent, but the degree of transparency could significantly affect the price.

Translucent – Materials that disrupt the passage of light. Some light will pass through a translucent material, but an object or writing placed behind it will be blurry. Some diamond crystals, even when of gem quality may be translucent.

Opaque – Materials that allow no light to pass through them. Black diamonds may be opaque as would some industrial grade diamonds.

Clarity and transparency are interconnected, but they are different. If there is a cloudy spot in a transparent diamond, the cloud is classed as a clarity feature. However, if the entire diamond is cloudy due, for example, to sub microscopic inclusions, then the cloudiness is a transparency feature.

To check for transparency, examine the diamond at different angles and check to see if it is clear. Face-up the diamond should be brilliant and there should be a strong contrast between dark and bright areas. When judging transparency make sure that the diamond is clean, as diamonds attract dirt and fingerprints which could lead to a more cloudy appearance.

You should be able to spot diamonds with serious transparency problems with the naked eye. They appear cloudy and will not sparkle or shine even under a jewellers optimised lighting conditions.