Diamond Fluorescence

When we speak of Diamond Fluorescence, we are referring to the diamonds tendency to emit a soft colored glow when subjected to ultraviolet light (such as a "black light").

Before going into the details of fluorescence, here's our overall opinion: the simple existence or absence of fluorescence should not influence your decision to purchase a diamond.

Diamond Fluorescence is a hotly debated topic in the diamond industry, but a 1997 study by the GIA suggests fluorescence makes very little difference to the appearance of the diamond.

In the diamond industry, the existence of fluorescence in a diamond (caused by the natural mineral properties of the diamond), has caused many debates and has, in many instances, influenced the pricing of diamonds.

Natural Light UV Light

It is common to find that diamonds with colorless grades (D-E-F) or near colorless grades (G-H-I-J) are lower in price when they exhibit fluorescence and faint yellow grades (K-L-M) are higher in price when exhibiting fluorescence.

The "theory" has been that: 1) fluorescence has a negative impact on colorless diamonds (making them appear cloudy) and 2) a positive impact on faint yellows (blue fluorescence supposedly counter-balancing the yellow color and making the diamond appear whiter).

Given the results of a 1997 GIA study on the effect of ultraviolet fluorescence on a diamond's appearance, we tend to toss the first half of that theory out the window and give slightly less credence to the second half.

The GIA study selected a group of similarly graded diamonds with varying degrees of fluorescence to be observed and commented on by study participants. Participants in the study included: trained diamond graders, trade professionals (e.g., jewelers), and average observers (general jewelry buying public).

Here's a quote from the study:

"For the average observer, meant to represent the jewelry buying public, no systematic effects of fluorescence were detected. Even the experienced observers did not consistently agree on the effects of fluorescence from one stone to the next.

"In general, the results revealed that strongly blue fluorescent diamonds were perceived to have a better color appearance when viewed table-up [ed: right-side up, as when placed in a setting] with no discernible trend table-down [ed: upside-down]. Most observers saw no relationship between fluorescence and transparency."

In other words, for the average observer fluorescence made no difference and experienced observers (diamond graders and trade professional) did not agree on the influence of fluorescence. And contrary to previous theories, the experienced/trained observers most consistently determined that diamonds with strong fluorescence were the ones with the best color.

Bottom Line on Fluorescence

Don't let flourescence unduly influence your choice when selecting a diamond.

If industry experts can't agree on the influence of flourescence and constantly split hairs over its effect, we feel it falls into the range of minutiae that simply serves to confound and confuse, rather than inform the diamond buying public.

However, because of industry debate and prejudice (which appears unfounded), you may find colorless or near-colorless diamonds that exhibit fluorescence have slightly lower prices than those that do not. Our opinion? Enjoy the lower price.

Of course, if you are buying diamonds as an investment and intend resale, you'll want to pay attention to how the industry prices diamonds with fluoresence -- independent of whether the price difference is justified.

Source : http://www.thediamondbuyingguide.com

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4 Cs Of Diamonds

Various characteristics of diamonds are graded and categorized by the diamond industry. Learning about diamonds is first learning about the "four Cs" of diamonds which are considered the most important grades and categories:

Cut
Clarity
Color
Carat weight

These are the criteria jewelers use when grading diamonds, and they're the ones you'll need to understand to buy the right diamond for you.

And then there's the "Fifth C":

Certificates















Diamond Cut

Don't confuse the diamond's "cut" with the diamond's "shape."

First, don't confuse diamond "cut" with "shape." Shape refers to the general outward appearance of the diamond, (such as round, emerald, or pear). When a diamond jeweler (or a diamond certificate) says "cut," that's a reference to the diamond's reflective qualities, not the shape (or at least it should be, we have found that even some "jewelers" don't appear to know the difference between "cut" and "shape").

The quality of the "cut" does make a difference in how a diamond looks.

Diamond cut is perhaps the most important of the four Cs, so it is important to understand how this quality affects the properties and values of a diamond. A good cut gives a diamond its brilliance, which is that brightness that seems to come from the very heart of a diamond. The angles and finish of any diamond are what determine its ability to handle light, which leads to brilliance.

(See Diamond Anatomy for an explanation of the terms used in the next paragraphs.)

As shown in the images below, when a diamond is well-cut, light enters through the table and travels to the pavilion where it reflects from one side to the other before reflecting back out of the diamond through the table and to the observer's eye. This light is the brilliance we mentioned, and it's this flashing, fiery effect that makes diamonds so mesmerizing.

In a poorly cut diamond, the light that enters through the table reaches the facets and then 'leaks' out from the sides or bottom of the diamond rather than reflecting back to the eye. Less light reflected back to the eye means less brilliance.

Good Proportions are Key
Most gemologists agree that the best cut diamonds are those that follow a set of formulae calculated to maximize brilliance. These formulae can be seen in a diamond's proportions, most importantly how the depth compares to the diameter, and how the diameter of the table compares to the diameter of the diamond.

If you opt to buy a diamond without an AGS certificate, spend some time looking at certified diamonds (where you know the Cut Grade) and train your eyes to identify the better cuts (by their "sparkle"). Cut does make a difference to the outward appearance of a diamond.

However, the variance in the proportions between an Ideal Cut and a Poor Cut can be difficult to discern by the casual observer.

Because cut is so important, several grading methods have been developed to help consumers determine the cut of a particular diamond. In general, these grades are:

Ideal
Premium
Very Good
Good
Fair & Poor

Which Grade of Cut Should I Buy?
Selecting the grade of cut is really a matter of preference. To make the best selection, you need to understand the various grades. Please note that the descriptions below are general guidelines.

Ideal Cut
This cut is intended to maximize brilliance, and the typically smaller table sizes of these diamonds have the added benefit of creating a great deal of dispersion or 'fire' as well. Ideal quality diamonds are truly for the person who enjoys knowing that he has one of the finest things that money can buy. This category applies only to round diamonds.

Premium
In the case of round diamonds, many Premium Cut diamonds have cuts that are the equal of any Ideal Cut diamond, though they often can be purchased at slightly lower prices than AGS Ideal Cuts. They are intended to provide maximum brilliance and fire. Like the Ideal Cut, these are also for the person who enjoys knowing that he has one of the finest things that money can buy.

Very Good
These diamonds reflect most of the light that enters them, creating a good deal of brilliance. With these diamonds, the cutters have chosen to stray slightly from the preferred diamond proportions in order to create a larger diamond. The result is that these diamonds fall slightly outside of some customers' preferences in terms of, for example, table size or girdle width, though, in many cases many of the parameters of diamonds in this range will overlap with certain parameters of diamonds in the Ideal or Premium ranges. Generally, the price of these diamonds in slightly below that of Premium cuts.

Good
Diamonds that reflect much of the light that enters them. Their proportions fall outside of the preferred range because the cutter has chosen to create the largest possible diamond from the original rough crystal, rather than cutting extra weight off to create a smaller Premium quality diamond. Diamonds in this range offer an excellent cost-savings to customers who want to stay in a budget without sacrificing quality or beauty.

Fair & Poor
A diamond graded as fair or poor reflects only a small proportion of the light that enters it. Typically these diamonds have been cut to maximize the carat weight over most other considerations.

Diamond Anatomy
Wondering what on earth is the diamond's pavillion? Table? Culet? The graphic and supporting text below explain the various "parts" of a diamond.














Diameter
The width of the diamond as measured through the girdle.

Table
This is the large, flat top facet of a diamond.

Crown
The upper portion of a cut gemstone, above the girdle.

Girdle
The narrow rim of a diamond that separates the crown from the pavilion. It is the largest diameter to any part of the stone.

Pavilion
The lower portion of the diamond, below the girdle. It is sometimes referred to as the base.

Culet
The tiny facet on the pointed bottom of the pavilion, which is the portion of a cut gem below the girdle.

Depth
The height of a gemstone, from the culet to the table.

Source : http://www.thediamondbuyingguide.com

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