Diamond Buyers Guide

First, a geology lesson: diamonds are 99.95% pure crystallised carbon and can be extremely old - one to three billion years old, in fact. They are the hardest naturally occurring substance known and are formed some 100 miles beneath the Earth's surface when crystals of diamond occur in volcano feed-pipes. When volcanoes erode down, they release diamonds from their feed-pipes into layers of gravel which are later mined. However, due to the relative rarity of this natural process, diamond mines are found in just a handful of sites around the world.

In rough form, diamonds are shipped to the world's cutting centres to be shaped and polished before being set as jewellery. It is the hardness, brilliance and sparkle that emerges during this process that transforms them into a girl's best friend.

The 4 Cs – Cut, Colour, Clarity and Carat provide a way of grading & certifying diamonds. It is these characteristics that determine the value, rarity and beauty of every diamond. Understanding the 4 Cs is a key part of choosing the right diamond for your taste and budget.

Once you've familiarised yourself with each of the 4 Cs, you will be able to decide which ones are the most important to you when making your choice.

Until the middle of the twentieth century, there was no agreed-upon standard by which diamonds could be judged. The Gemological Institute of America created the first globally accepted standard for describing diamonds: Colour, Clarity, Cut, and Carat Weight. Today, the 4Cs of Diamond Quality is the universal method for assessing the quality of any diamond, anywhere in the world.

The creation of the Diamond 4Cs meant two very important things: diamond quality could be communicated in a universal language, and diamond customers could now know exactly what they were about to purchase.

We would however suggest you consider a 5th C - Certification, further ensuring that your diamond is exactly the stone you want and offering additional confidence in the purchase.

Diamond Shapes

Round brilliant Cut Diamond

Round Brilliant

The most brilliant of all shapes, the Round Brilliant is the most popular diamond shape, representing over 70% of all diamonds sold.

Princess Cut Diamond


The next most popular shape is the square-shaped Princess. Exquisite in both name and brilliance, a princess-cut diamond’s “V” pavilion facets are a sight to behold under a microscope.

Emerald  Cut Diamond


The emerald cut was originally designed for the cutting of emeralds but was found to work perfectly for diamonds, enhancing their lustre.

Oval Cut Diamond


Created by Lazare Kaplan in the 1960's, oval diamonds are a modified brilliant-cut. The oval is an ideal choice for a customer who likes the look of a round diamond, but wants something more unique.

Asscher Cut Diamond


First made popular during the Art Deco era, a perfectly symmetrical diamond with spectacular beauty, scintillation and brilliance.

Pear Cut Diamond


The pear diamond has a brilliant cut which optimises light reflection, and combines the shape of an oval and marquise diamond.

Asscher Cut Diamond


The marquise shape stone is an elongated shape with pointed ends. This shape looks spectacular on longer fingers.

Heart Cut Diamond


The heart shaped diamond is pear shaped with a cleft cut into its top. A complex cut with 56 to 58 facets & demands a great amount of skill to ensure maximum brilliance.

Radiant Cut Diamond


The Radiant shape diamond combines the elegance of the Emerald-cut with the brilliance of the Round Brilliant.

Cushion Cut Diamond


Popular during the Victorian era, this rare cut, also known as the pillow cut diamond, has a square or rectangular shape with rounded corners.

Diamond Colour

Diamonds come in a variety of colours, some of them highly prized (pinks, blues, even yellow). In a white diamond, however, the presence of a yellow tint will lower the price of a diamond. The less body colour in a white diamond, the more true colour it will reflect, and thus the greater its value.

Diamonds are assigned a colour grade by the GIA in a viewing environment specially designed to eliminate colour from surrounding surfaces as well as the light source itself.

This allows the colour of the diamond to be accurately measured. Minor differences in diamond colour detected in this environment are very difficult, if not impossible, to detect in a normal environment.

The diamond industry has adopted the GIA diamond colour scale; almost every diamond sold today is rated using the GIA colour scale, whether it was actually certified by the GIA or not.

Colourless D E F

While there are differences in colour between D, E, and F diamonds, they can be detected only by a gemologist in side by side comparisons, and very rarely by the untrained eye.

D-F diamonds should only be set in white gold / platinum. Yellow gold reflects colour, negating the diamond's colourless effect.

My Image

D to F

Near Colourless G H

While containing traces of colour, G-J diamonds are suitable for a platinum or white gold setting, which would normally betray any hint of colour in a diamond.

Because I-J diamonds are more common than the higher grades, they tend to be a great value. An I-J diamond may retail for half the price of a D diamond. Within the G-J range, price tends to increase 10-20% between each diamond grade.

My Image

G to H

Faint Colour

Beginning with K diamonds, colour (usually a yellow tint) is more easily detected by the naked eye. Set in yellow gold, these warm coloured diamonds appeal to many, and are exceptionally valuable.

Due to its perceptible colour tint, a K diamond is often half the price of a G diamond.

My Image

I to J

My Image

K to M

Very Light Colour

Diamonds in the N-R colour range have an easily seen yellow or brown tint, but are much less expensive than higher grades.

For almost all customers, S-Z diamonds have too much colour for a white diamond.

My Image

N to R

My Image

S to Z

What is ultraviolet fluorescence?

Fluorescence is the visible light some gemstones emit when they are exposed to invisible ultraviolet (UV) rays. In natural diamonds, blue is the most common colour of fluorescence, but other colours may be visible.
On a GIA Diamond Grading Report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to long-wave UV, which is an essential component of daylight.


Colour becomes much harder to detect once a stone is set in a ring and placed in an environment that contains colour (as opposed to the all white background used in diamond colour grading). For instance, an H colour diamond may look as colourless as a D when set in a ring under normal lighting conditions, especially if the two are not compared side by side.

Another factor that affects a diamonds's apparent colour is the colour of the mounting itself. Yellow gold makes slight amounts of yellow in a diamond less obvious, while white metal mountings make the colour in yellow diamonds more apparent.

The vast majority of untrained observers (and many gemologists) cannot distinguish a colour grade from the one just above or below unless the diamonds are compared side by side in a controlled environment.

Colour becomes more important as carat weigh increases. Colour is easier to perceive in a larger diamond, just as a carafe of white wine shows more colour than a single glass.

Carat Weight

Diamond carat weight is the measurement of how much a diamond weighs.

A metric "carat" is defined as 200 milligrams.

Each carat can be subdivided into 100 'points.' This allows very precise measurements to the hundredth decimal place. A jeweller may describe the weight of a diamond below one carat by its 'points' alone. For instance, the jeweller may refer to a diamond that weighs 0.25 carats as a 'twenty-five pointer.' Diamond weights greater than one carat are expressed in carats and decimals. A 1.08 carat stone would be described as 'one point oh eight carats.'

All things being equal, diamond price increases with diamond carat weight, because larger diamonds are rarer and more desirable. But two diamonds of equal carat weight can have very different values depending on the other diamond 4Cs: Clarity, Colour, and Cut.

How did the system start?

The modern carat system started with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales. The carat is the same gram weight in every corner of the world.

The word "carat" was possibly derived from the Greek word kerátion literally meaning a small horn, and refers to the carob seed as a unit of weight.

What are "magic sizes"?

Some weights are considered "magic sizes" – half carat, three-quarter carat, and carat.

Visually, there is little difference between a 0.99 carat diamond and one that weighs a full carat.But the price differences between the two can be significant.

Diamond Cut

Cut refers not to a diamond's shape (e.g. round, oval, pear, etc.) but to a diamond's proportions, symmetry and polish. The beauty of a diamond depends more on cut than any other factor. Though extremely difficult to analyse and quantify, diamond cut has 3 primary effects on appearance: Brilliance (the brightness created by the combination of all the white light reflections from the surface and the inside of a polished diamond), Fire (the dispersion of light into the Colours of the visible spectrum, seen as flashes of colour), and Scintillation (the flashes of light and dark, or sparkle, when a diamond or light source is moved).

When a diamond is fashioned from a rough stone, the cutter must balance optimal cut (and therefore appearance) against maximum yield (cutting the diamond to maintain as much carat weight from the rough stone as possible). Because many customers are willing to pay more for a larger, fair-cut cut diamond than for a slightly smaller, well-cut diamond, there is pressure on the cutter to sacrifice appearance for weight. This is why the Cut grade is so important; it allows the purchaser to identify those stones that were cut Fair to Poor in an effort to gain carat weight.


Diamond proportion refers to the relationship between the size, shape, and angle of each facet of a diamond. A wide range of combinations are possible, ultimately determining the diamond's interaction with light.

When light strikes a diamond, approximately 20% immediately reflects off the surface (as glare). Of the 80% that enters, a portion will escape through the bottom of the diamond (where the observer cannot appreciate it). A well proportioned diamond will have each facet properly placed and angled so as to maximize the amount of light that reflects back out of the crown (top) of the diamond, to the eye of the observer. This reflected light is perceived as scintillation, fire and brilliance.

Most gemologists agree that the best cut diamonds are those that follow a set of formulae calculated to maximise 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.

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 Cut

This cut is intended to maximise 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.


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 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 amount 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.


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 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 maximise the carat weight over most other considerations.

Diamond Clarity

Because they are formed deep within the earth, under extreme heat and pressure, virtually all diamonds contain 'birthmarks'; small imperfections inside the diamond (called inclusions) or on its surface (called blemishes).

Clarity refers to the degree to which these imperfections are present. Diamonds which contain numerous or significant inclusions or blemishes have less brilliance because the flaws interfere with the path of light through the diamond.

The position of an inclusion affects how easily it can be seen. Diamond cutters make every effort to cut a stone so that inclusions are not visible through the table of the finished diamond.

The preferred position for inclusions is under the bezel facets or near the girdle because they are harder to see there.

Almost all diamonds are graded for clarity using the 11 point diamond clarity scale created by the GIA, including diamonds which were not actually graded by GIA (every diamond we use is GIA certified). In grading diamond clarity, the GIA considers the number, size, colour, reflectivity, and position of every flaw visible under 10x magnification.


Flawless: No inclusions or blemishes are visible to a skilled grader using 10x magnification.

Extremely rare; less than 1 in 5,000 jewellery quality diamonds are rated FL.


Internally Flawless: No inclusions, only blemishes are visible to a skilled grader using 10x magnification.

FL and IF diamonds appear identical unless viewed under 10x magnification by a skilled grader. Less than 3% of jewellery quality diamonds are rated IF.


Very, Very Slightly Included: Inclusions are difficult for a skilled grader to see under 10x magnification.

VVS1 inclusions are typically only visible from the pavilion, while VVS2 inclusions are visible from the crown. In each, the inclusions are invisible to the eye, appearing identical to the higher grades unless viewed under 10x magnification by a skilled grader.


Very Slightly Included: Inclusions are clearly visible under 10x magnification but can be characterised as minor.

Inclusions are not visible to the naked eye. Perhaps 1 in 100 untrained observers can detect VS2 inclusions with the naked eye, on close inspection under ideal conditions.


Slightly Included: Inclusions are noticeable to a skilled grader using 10x magnification.

SI1 is the lowest grade with flaws often invisible to the naked eye. SI2 inclusions are usually visible to the naked eye, although they will require close inspection.


Included: Inclusions are obvious under 10x magnification and may affect transparency and brilliance.

I1 diamonds have inclusions that are almost always visible to the naked eye. I2-I3 diamonds have pronounced inclusions, and in the case of I3 may even affect the diamond's durability.


Precious metals are rarely used in their pure form, as they are too soft. Gold, silver, platinum and palladium are generally mixed (alloyed) with copper or other metals to create an alloy that is more suitable to the requirements of the jeweller or silversmith. The hallmark indicates the amount of precious metal in the alloy in parts per thousand (the millesimal fineness). In addition to indicating the town where the item was marked, a unique sponsor’s or maker’s mark identifies the item’s origin and a date letter to represents the year of marking.

All of our products come with a guarantee of the precious metal content through the 700-year-old practice of third party independent hallmarking.

This is a quality control mark placed on gold, silver and platinum and it's a safeguard for purchasers. Basically, the hallmark shows that it has been tested by an independent body (at the Assay Office) and guarantees that the metal is of one the legal standards of fineness (purity).

A hallmark also lets your jeweller quickly check what carat your jewellery is if you have to take it in for repairs or alterations. It is a legal requirement for most articles of precious metal above a certain minimum weight to carry an approved hallmark.

The British hallmark is made up of at least 3 compulsory symbols:

The Sponsor's Mark
This indicates the manufacturer, or sponsor of the item. This consists of the initials of the company who sent in the item for assaying.

The Fineness Mark
This indicates what the metal is and its standard of purity in parts per thousand.

The Assay Office Mark
This identifies the Assay Office at which the item was tested and marked.


The Goldsmiths’ Company Assay Office in London (also known as Assay Office London or the London Assay Office) is the oldest assay office in the United Kingdom.

The company has provided hallmarking services since the Goldsmiths’ Company was founded in the 1300s.

The company received its royal charter in 1327 and ranks 5th in order of precedence of the 12 Great Livery Companies of the City of London.


Hallmarking dates back to the 1300s, when Edward I of England passed a law requiring any item made of silver and offered for sale to be at least of equal quality as that of the coin of the realm (silver currency).

The four wardens of the Goldsmiths’ Company were tasked with visiting workshops in the City of London to assay (test) silver articles.


If these articles were found to be below standard they were originally forfeit to the King, but if they passed, each article received the King’s mark of authentication which was the mark of a leopard’s head. By 1478, there were several hundred workshops and merchants manufacturing silver articles in the City of London. It was not possible for the wardens to visit them all, and so the merchants were ordered to bring their items to Goldsmiths’ Hall for testing and marking, with a permanent Assay Office being established in the building.

This is the origin of the term hallmark – struck with the King’s mark at the Goldsmiths’ Hall.

In 1544, the Goldsmith’s Company adopted the King’s mark as their town mark, and the mark of the leopard’s head is now internationally recognised as the mark of this assay office.

GIA Certification

The Gemological Institute of America, or GIA, is a nonprofit institute dedicated to research and education in the field of gemmology and the jewellery arts.

Founded in 1931, GIA's mission is to protect all buyers and sellers of gemstones by setting and maintaining the standards used to evaluate gemstone quality. The Institute does so through research, gem identification, diamond grading services and a variety of educational programs.

Through its world-renowned library and subject experts, GIA acts as a resource of gem and jewellery information for the trade, the public and worldwide media outlets.

In 1953, the GIA developed its International Diamond Grading System and the Four Cs (cut, clarity, colour, and carat weight) as a standard to compare and evaluate the quality of diamonds.

Today, the institute is headquartered in Carlsbad, California and operates out of 13 countries, with 11 campuses, 9 laboratories and 4 research centres worldwide.

The GIA set the standard for diamond grading and gemmological identification, and their grading system serves as the international gem and jewellery industry's benchmark credentials.

Shape and Cutting Style: The diamond shape and cutting style.

Measurement: Lists the diamond's dimensions in millimetres.

Carat Weight: The weight of diamond listed to the nearest hundredth of a carat.

Colour Grade: A grading which assesses the absence of colour in a diamond.

Clarity Grade: Clarity grade determined under 10x magnification.

Cut Grade: A grade of cut as determined by a diamond's face-up appearance, design and craftsmanship. A cut grade is available on round diamonds graded after Jan. 1, 2006.

Finish: Grades that represent a diamond's surface and facet placement.

Polish: Rating the overall smoothness of the diamond's surface.

Symmetry: Measuring the shape, alignment and placement of the diamond's facets in relation to one another as well as the evenness of the outline.

Fluorescence: Colour, and strength of colour when diamond is viewed under UV light.

Comments: A description of additional diamond characteristics not already mentioned in the report.

Clarity Plot: A map of the approximate size, type, and position of inclusions as viewed under a microscope.

Proportion Diagram: A map of the diamond's actual proportions.

Victoria Barker Fine Jewellery | GIA Certification
Victoria Barker Fine Art Jewellery of London

All rights reserved 2023 - Victoria Barker Fine Jewellery

All rights reserved 2023 - Victoria Barker Fine Jewellery