My Cart


The gallery at 44 Ann Street

Ballycastle BT54 6AD is now closed

Online sales only or contact us to visit our workshop

SHOP ONLINE: Free UK Delivery

On orders over £50

How to Select your Diamond

Diamonds - how to select them and know that you are buying quality - four factors: the cut, the colour, the clarity and carat weight

At Robert Spotten Jewellery Design, we like our customers to have nice quality diamonds. We have carefully selected our suppliers in order to achieve this even in the case when no certificate is required.

The quality of diamonds we purchase are always a minimum G/H colour and Si clarity.

What can you find out about your diamond? GIA provides an excellent guide which has been summarized below:

Diamonds come in many sizes, shapes, colors, and with various internal characteristics.
Diamond professionals use the grading system developed by GIA in the 1950s, which established the use of four important factors to describe and classify diamonds: Clarity, Color, Cut, and Carat Weight.
Different Shaped Diamonds

Diamonds can be fashioned into a variety of shapes and still be beautiful.

These are known as the 4Cs. When used together, they describe the quality of a finished diamond. The value of a finished diamond is based on this combination.

A diamond’s value is often affected by the rarity of one or more of the 4Cs. 
Subtle differences in color can dramatically af­fect diamond value. Two diamonds of the same clarity, weight, and cut can differ in value based on color alone. Even the slightest hint of color can make a dramatic difference in value.

Colorless Diamond

This emerald cut diamond is colorless and is a D color grade. – Courtesy Lazare Kaplan Diamonds

Diamond Color and Value Chart

In the normal colour range, the closer a diamond gets to colourless, the higher its per-carat price.

Diamonds come in many colours. Diamonds that range from colourless to light yellow and brown fall within the normal colour range. 

Diamond Examples on the GIA Color Scale

These diamonds—graded E, K, and Z—represent diamond colours near the top, middle, and bottom of the GIA Colour Scale. - © GIA & Tino Hammid

Diamond Color

To eliminate the guesswork from grading a diamond’s color, graders compare it to masterstones that represent known colors in the GIA D-to-Z scale. - © GIA & Tino Hammid

The GIA D-to-Z scale is the industry standard for colour-grading diamonds. Each letter represents a range of colour based on a diamond's tone and saturation.

Many diamonds emit a visible light called fluorescence when they’re exposed to ultraviolet (UV) radiation.  
Blue is the most common fluorescent color in gem-quality diamonds. In rare instances, fluorescence can be white, yellow, orange, or many other colors.
Strong blue fluorescence can make a light yellow diamond look closer to colorless in sunlight. Blue and yellow are color opposites and tend to cancel each other out, so blue fluorescence masks the yellow color. If the fluorescence is too strong it can make the stone look cloudy or “oily,” which can lower the value of the diamond. 

Diamonds have internal features, called inclusions, and surface irregularities, called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of inclusions and blemishes.
Among other things, blemishes include scratches and nicks on a diamond’s surface. Inclusions are generally on the inside, and some might break the surface of the stone. Sometimes, tiny diamond or other mineral crystals are trapped inside a diamond when it forms. Depending on where they’re located, they might remain after the stone has been cut and polished, and they can affect a diamond’s appearance.
Clarity characteristics might have a negative influence on a diamond’s value, but they can have positive effects as well. For one thing, they help gemologists separate diamond from imitations. (This is easier with included diamonds than with flawless ones.) And because no two diamonds have exactly the same inclusions, they can help identify individual stones. They can also provide scientists with valuable information about how diamonds form.

Identifying Diamonds

Like the rest of the 4Cs, clarity’s influence on value is directly related to the concept of rarity. Flawless is the top grade in the GIA Clarity Grading System. Diamonds graded Flawless don’t have visible inclusions or blemishes when examined under 10-power (10X) magnification by a skilled and experienced grader.

Diamond Clarity and Value Chart

As clarity increases, and if all other value factors are equal, diamond price per carat also increases.

Flawless diamonds are very rare—so rare, in fact, that it’s possible to spend a lifetime in the jewelry industry without ever seeing one, and they command top prices.
At the other end of the scale are diamonds with inclusions that can be easily seen by the unaided eye. Between the two extremes are diamonds with inclusions visible only under 10X magnification. Stones in the middle range make up the bulk of the retail market.

There are 11 clarity grades in the GIA clarity grading system. They are Flawless, Internally Flawless, two categories of Very, Very Slightly Included, two categories of Slightly Included, and three categories of Included.
The effect of a clarity characteristic on the clarity grade is based on its size, number, position, nature, and color or relief.

Diamond Clarity Grade

Diamond professionals use a set of terms that originally included very very slightly imperfect, very slightly imperfect, slightly imperfect, and imperfect. In recent years, the term imperfect has been replaced with included. (GIA uses included in its clarity grading system.)
These terms were shortened to the initials VVS, VS, SI, and I. The abbreviations eventually gained acceptance throughout the international diamond community. Their use is now widespread regardless of how the words they stand for translate into various languages. Very may translate to tres in French, for instance, but in France a very slightly included diamond is still a VS. Even a country like Russia, with a completely different alphabet, uses the same abbreviations.

A beautifully finished diamond is dazzling, with every facet displaying the craftsman’s skill and care. When a diamond interacts with light, every angle and every facet affects the amount of light returned to the eye. This is what gives it its face-up appearance.

1.54 Ct Diamond

A diamond’s proportions determine how light performs when it enters the diamond. If light enters through the crown and goes out through the pavilion, the diamond will look dark and unattractive.  Diamonds with different proportions and good polish make better use of the light, and will be bright, colorful, and scintillating.

Well-cut Diamond
A well-cut diamond displays the beauty consumers expect to see in a diamond.

Brightness in a Diamond
As a general rule, the higher the cut grade, the brighter the diamond. Under fluorescent lighting, these diamonds (left to right) display high, moderate, and low brightness.
The term “cut” also can describe a fashioned diamond’s shape. Shapes other than the standard round brilliant are called fancy cuts. The best known are the marquise, princess, pear, oval, heart, and emerald cut.

Various Diamond Shapes

Fancy-shape diamonds, along with the classic round diamonds, are popular choices for today’s jewelry consumer. Courtesy Lazare Kaplan Diamonds

Carat Weight
Diamond weights are stated in metric carats, abbreviated “ct.” One metric carat is two-tenths (0.2) of a gram—just over seven thousandths (0.007) of an ounce. A small paper clip weighs about a carat.

The metric carat is divided into 100 points. A point is one hundredth of a carat.
Over a carat, diamond weights are usually expressed in carats and decimals. A 1.03-carat stone, for example, would be described as “one point oh three carats,” or “one oh three.” Weights for diamonds that weigh under a carat are usually stated in points. A diamond that weighs 0.83 carat is said to weigh “eighty-three points,” or called an “eighty-three pointer.”

100.20 Ct. Diamond

Large high quality diamonds are rare and valuable gems. This diamond weighs a remarkable 100.20 carats and is internally flawless. - © GIA and Harold & Erica Van Pelt, courtesy The Steinmetz Group

Large diamonds are more rare than small diamonds. The more scarce something is, the more it is worth. So a larger stone doesn’t just cost more. It also costs more per carat. A 1-carat diamond weighs the same as four 0.25-carat diamonds. But even if all the other quality factors are equal, the larger diamond is worth much more than the sum of the four smaller diamonds.

Oval Shape Diamond

This oval shape diamond weighs 1.01 carats and made the 1.00 carat magic size range. When diamonds reach the so called magic sizes the value per carat increases. – Courtesy Lazare Kaplan Diamonds

Don’t confuse the term carat with karat. Karat is a unit of measure used to describe how much pure gold there is in an alloy.

Attention Different laboratories test and grade diamonds, the most stringent being the GIA. Price of diamonds will be affected by the laboratory which supplied the certificate, GIA certificates being the most expensive.

Other stones look like diamonds. In the past some of our customers have been duped into buying "diamond" jewellery online, thinking they were buying a real diamond. Beware of expressions such as "CZ diamond" or "Manmade diamond" which describe synthetic stones.

White Sapphire

The white sapphire can replace the diamond, with a slightly lesser durability than the diamond.

White Topaz

The white topaz is a semi-precious stone which can look like a diamond but it is softer and therefore less durable.


Moissanite is a synthetic stone with quite a high hardness score, it is the closest imitation to diamond. It can appear more brilliant than diamond and sparkle with more colours when the light enters the stone.

Cubic zirconia (CZ)

Cubic zirconia is a form of zirconium dioxide and is created synthetically. It is the most common diamond substitute but gets easily scratched due to its softness.


A mineral, the spinel can replace a diamond but is even softer than the CZ.