Thursday, January 24, 2013

What about Fluorescence?

We are frequently asked about what fluorescence in a diamond is, and how it affects pricing.  Well, the simple answer is not quite so simple.  About half of the world’s diamonds production has fluorescence that can be observed under when illuminated with a long wave ultra violet light.

 

About 10% of the diamonds on the market have florescence that is strong enough to make a noticeable difference between the stone's color in incandescent light which is low in uv light. and in sunlight or fluorescent light which are high in uv.  When a diamond has fluorescence it is classified in intensity as being faint, medium, strong or very strong.  In almost all cases that fluorescence color seen under UV light is blue in color.  this is highly important, as blue fluorescence negates or minimizes the appearance of yellow.

 

If the diamond being considered for purchase is high color, say a D to G colored gem, it tends to be lower in wholesale price due to the presence of fluorescence.  How much lower that price depends primarily if it has a waxy or somewhat milky white appearance due to the fluorescence.

 

If the stone is H to I in color fluorescence likely has little or no impact on the gem’s price, again unless it exhibits that waxy appearance.

 

As the stone’s color grade drops to the J to M in color range the presence of blue fluorescence may have a beneficial impact on the stone’s appearance of color, and may help the stone bring a higher retail price.

 

When we are looking at loose, unmounted diamonds in our office the stones are typically presented in a small folded envelope called a flute.  These diamond paper flutes are lined with a blue colored paper liner, which makes the gems contained inside appear whiter than they actually are. 

 

Retail dealers usually show these loose gems on a blue or dark colored felt pad, which also makes them, look whiter.

 

Ask to see the stone upside down on a folder piece of white paper, with the white paper below and behind the gem.  This is the best way to determine if a stone had body color and if it is a darker or lighter hue that another gem place next to it on the paper.