Since I've put together this website there has been one subject I forgot to address in detail.  I've received more questions regarding fluorescence in diamonds than just about everything.  So here's the dirt from soup to nuts on fluorescence.

What is it?

Florescence is the results from the interaction between a light's energy and the atoms in a diamond.

How does it happen?

Diamond is crystallized carbon. This process happens about 75-125 miles below the surface of the earth and usually where volcanic or ancient volcanic sites exist where there was a lot of heat and pressure in the earth.  If there are traces of the mineral boron present in the earth as this crystallization process is occurring the diamond will fluoresce. The various colors that diamonds can fluoresce can be blue, yellow, green, orange and white. Blue is the most common.

Do all diamonds have fluorescence?

No.  About 50% of the diamonds produced actually have florescence that can be observed under special conditions like under a long wave ultra violet light. 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 either faint, medium, strong or very strong.

So is fluorescence in diamond a good or bad thing?

Well, it can be either good or bad depending on a couple of factors.  Generally fluorescence in diamond is neutral in most circumstances.  Here are some points where fluorescence can be a positive thing.

1. If a diamond is tinted in color (like K, L or lower on the color scale) fluorescence in a diamond can make the color look better than what it actually is. =)

2. If you are considering the purchase of high clarity and high color diamonds fluorescence can bring down the cost (saving you a few bucks) even if the fluorescence is not so noticeable ;)

3. If you want to consider this a positive... you can now tell you're grandma you got a "blue white".  Hehe... if you ever hear some old timers telling you they got a "blue white" diamond, chances are they got snowed (but not all the time though).  Back in the 70's and earlier colorless diamonds (D-F colors) were called "blue white" because of their exceptional color.  Many diamond scammers were taking diamonds with strong blue fluorescence (with colors lower than "F") and were selling them as "blue white" diamonds.  The FTC issues a warning to those who abuse that term in a sales transaction.

Times when fluorescence can be a bad thing.

1. When jewelers misrepresent the true color of the diamond and try to sell it as something it isn't. Not too long ago I was helping a young man and I lost the sale to another diamond broker in the city.  The customer, BEFORE THE SALE, actually called me from the city and told me about the deal the merchant was offering him.  He was going to get a 1.03ct round diamond, H color, SI1 clarity for $3,500.  My advice was to buy it (if indeed that's what it really was) BUT MAKE SURE that it was backed with FULL CASH REFUND FOR ANY REASON. Remember... when it sounds too good to be true...  In his excitement he didn't get this in writing and bought the stone.  He brought it in for me to examine and appraise and sure enough... he bought a diamond that was O in color and SI1 in clarity BUT WITH VERY STRONG FLUORESCENCE. As soon as we laid the stone face down on the flat white background it was obvious.  When I put the diamond under long wave uv light for the customer to see the diamond had VERY STRONG fluorescence. Under the jewelers lights the fluorescence was prominent and made his yellow stone look "blue white" in certain lighting.  Bottom line: he got ripped.

2. Fluorescence can also be bad if it is so strong that it alters the appearance of the diamond to a milky or oily look. Not in all diamonds but in about 10% of diamonds in the market place fluoresce so strong that the stone doesn't look as transparent as it should.  Diamonds with faint, medium or strong fluorescence generally don't do this but when you are looking at a diamond with "very strong" fluorescence, ask to be able to observe it next to a stone with lower or no fluorescence.  If you don't see a difference in the transparency then it's ok. I'm working on getting some comparison pictures up here so you can see this and I should be able to capture it.

So what does it look like?

First is a picture of 4 diamonds before turning on the long-wave uv light.  These are diamonds with 1. strong blue fluorescence, 2. medium blue, 3. faint and then none or Inert fluorescence.

Here's another 2 pictures of the same 4 stones but with more of the outside light being blocked.  Makes the fluorescence stand out more.

How does fluorescence affect the value of diamonds?

Fluorescence can affect value negatively or positively depending on the quality you're looking at.  Our friend Rappaport published an interesting table reflecting how fluorescence affects the various values in certain qualities of diamond.

As we can see from the above table diamonds that are IF - VS in clarity, D-H in color there is somewhat of a discount ranging from as high as 15% (in IF-VVS clarities, D,E colors) and down to 2% (in H VS).  Notice that if you are purchasing SI in clarity, fluorescence has virtually no impact on value at all except when you get into the I, J, K and lower the value is increased in the SI range.

Bottom line with fluorescence:

Don't let fluorescence discourage your purchase. ONLY if it is noticeably visible to the human eye making the stone look chalky should you consider turning down the purchase.  When you are purchasing, ASK if there is fluorescence. If there is "very strong" fluorescence ask if you can compare it with another and if you don't like what you see... don't buy.