Understanding Diamonds

The 4 C’s

This guide is here to help you gain an understanding on how to evaluate a diamond’s quality so that you can choose the diamond that best suits you and your budget.

Each diamond’s price is affected by a variety of factors. The globally accepted standard for evaluating diamonds is known as the 4 C’s: cut, colour, clarity and carat weight. We have analysed each of these factors individually for your convenience. Have a look and do not hesitate in contacting us if you have any further doubts!

Basic Diamond Terminology

Understanding the basic terminology of a brilliant cut diamond’s structure is pivotal. It allows us to gain a much better understanding of what the 4C’s are actually about. A brilliant cut diamond is one which is cut in a shape with several facets which resemble a cone.

  • Facet: Any of the “flat” sides of a diamond.
  • Table: The largest facet on the top of the diamond.
  • Crown: The section of the diamond extending from the table to the girdle.
  • Girdle: This is the ring at the widest part of a diamond, where the crown ends and pavilion begins.
  • Pavilion: The section of a diamond extending downward from the girdle to the culet point.
  • Culet: The bottom tip (it is actually a tiny facet) of a diamond.
  • Diameter: The width of a brilliant cut diamond measured from one side of the girdle to another.
  • Depth: The total height of the gemstone measured from the culet to the table.

Diamond Cut

The proportions of a diamond’s cut, its polish and symmetry will determine how much light it will reflect. These three factors are decisive in creating a diamond with the highest degree of light reflection. It is very simple, the better the cut, the more light the stone will refract and reflect back through the top of the diamond. A poor cut will result in light seeping out from the sides and bottom of the diamond (called light leakage) or it can limit the amount of light that enters the stone. This results in a dark and dull diamond regardless of whether the clarity and colour grades are high.

Cut Grade

  • Appearance Based Factors

    How good a diamond’s cut is, is dependent on a combination of three different types of reflection called brilliance, fire and scintillation that the cut creates. These are known as appearance-based factors. A high quality cut produces a diamond with brilliance, fire and scintillation and consequently, a high light return:

    • Brillance: when light hits a diamond, some is reflected back and some is goes through the stone. The angles of the diamond’s crown return most of the light. Brilliance refers to all the white light that is reflected back to the eye through the diamond’s top.
    • Dispersion or fire: these terms refer to a prism effect which occurs when white light enters a diamond and refracts into different colours. It is easier to see this phenomenon in places where the light is low.
    • Scintillation: describes the intense light or flashes produced when a diamond is tilted from side to side. Light which hits a diamond and is not reflected back immediately may bounce from the inside walls towards the diamond’s centre. The light which bounces off the inside walls leads to the phenomenon called ‘scintillation’.
  • Craftsmanship Based Factors

    A diamond’s proportion, symmetry and polish refer to the diamond cutter’s craftsmanship and design. The quality of a diamond’s cut is reliant on these craftsmanship factors and how beautiful a combination of brilliance, fire and scintillation they create.

    • Proportion: refers to the relationship between size, shape and angles of each of the diamond’s facets. For example, if a diamond is cut too shallow, the angle at which entering light strikes the pavilion will be too low, causing the light to refract and escape through the bottom of the diamond. In a well-proportioned diamond, light hits each pavilion at an angle which allows the majority of light to reflect back through the crown. Figure 1 below illustrates this phenomenon.
    • Symmetry: symmetrical diamond facets are crucial in order to maximise the amount of light which enters and exits the stone. Facets which are only a few degrees out of alignment affect brilliance, fire and scintillation.
    • Polish: After a diamond is cut, each facet is polished. A poor polish may scratch the facets and thus lower the grade of the cut.

  • Cut Grade
    • Ideal: The diamond will reflect nearly all the light that enters the stone.  Diamonds with a cut grade of ideal are very rare and extremely beautiful.
    • Very Good: Reflects almost as much light as those diamonds graded ‘ideal’ at a considerably lower cost. 
    • Good: These diamonds are usually cut to maximise size but are still of high quality and beauty.  Reflect most of the light that enters.  Cost much less than ‘Very Good’ cuts.
    • Fair: Reflect some light and maximises weight.  Still considered to be good quality diamonds. 
    • Poor: Usually cut too shallow or deep causing considerably light leakage out of the sides and base.    

Choosing a Cut

We recommend selecting the highest cut grade within your budget. The reason is simple: of the Four Cs, no other characteristic has a greater influence on a diamond's appearance.

Diamonds with the highest cut grades cost more, not only because they are rarer, but also because of the skill, experience and time needed by the diamond cutter to produce such a beautiful stone.

The sparkle of a well-cut diamond can actually make it appear larger than one might expect based on carat weight alone.

Diamonds with a cut grade of good or very good represent an excellent combination of beauty and value.

Diamond Colour

When discussing colour in white diamonds, experts refer to the stone’s body colour.  Completely colourless diamonds are composed of 100% pure carbon without any impurities.  Nevertheless, nearly all diamonds exhibit some degree of colour.  The majority of diamonds exhibit hints of yellow or brown, which is caused by the existence of nitrogen during the diamond’s formation process.  Ultimately, the rule is very simple.  The less body colour exhibited by a diamond, the rarer it is and thus, the higher its value.

Colour Grade

A diamond’s colour grade is based on its lack of colour.  The less body colour exhibited by a diamond, the more true colour it reflects, and the higher its colour grade.  The vast majority of diamonds are assigned a colour grade according to the Gemological Institute of America’s (GIA) diamond colour scale – whether certified by the GIA or not.  This is the international colour grade scale for diamonds.  The grading process involves examining a diamond face-down under a controlled light source.  The diamond is then compared to a “master stone” which has a predetermined colour.

Diamonds are graded from “D” for colourless, continuing through the alphabet to “Z”, for stones with very faint or light yellowish/brownish colour.  At Le Juelier, all of our diamonds have a J or higher colour grade.  All D-Z diamonds are white diamonds.  Actual coloured diamonds are known as “fancy diamonds” and are graded on a different scale.  Below is an annotated GIA colour scale:  

Colour grade diamond Le Juelier

  • Colourless (D, E, F)Differences in D, E and F diamonds are difficult to detect by the untrained eye.  D diamonds are 100% colourless and extremely valuable, whilst detecting colour traces in E-F diamonds is tremendously difficult.  They are very expensive.D-F diamonds are often set in white gold or platinum as yellow gold reflects colour and cancels out the diamond’s colourless effect.
  • Near Colourless (G, H, I, J)G-J diamonds have such a slight colour trace that they can still be set in white gold or platinum, despite these metals highlighting any colour trace in the diamond.  For the untrained eye, it is extremely difficult to detect the colour in these diamonds.

    Whilst still rare and of good value, these diamonds are more affordable than the D-F range diamonds.  There is usually a 10-20% price difference between each grade in the G-J range.

  • Faint Colour (K, L, M): Diamonds with a K colour grade and below have a slightly more yellow tint which is noticeable to the naked eye.   

     These diamonds are usually set in yellow gold where their colour can be hidden to a certain extent.  Diamonds in this range can also be beautiful.  As a result of their discernible colour, K diamonds are usually half of a G diamond’s price. 

  • Very Light Colour (N - R): The diamonds in this range have a easily noticeable yellow or brown tint.  Considerably cheaper than higher range diamonds.

Choosing a Colour Grade

After cut, the colour grading of a diamond is often considered the second most important quality when selecting a diamond. This is because the human eye tends to notice a diamond’s light return before noticing its colour.  As outlined briefly above, the type of metal in which a diamond is set in can complement its colour.  Consider a yellow gold setting for diamonds with a colour grading of I-J as they will appear whiter.  On the other hand, those diamonds which are near colourless or colourless are best complemented by white gold or platinum.

In this regard, you should always keep in mind that the visible difference between single diamond colour grades in smaller diamonds, for example G to H or I to J, is so minor that it is difficult to detect with the naked eye.  Yet, the cost difference is likely to be significant.  However, you must remember that the larger the diamond, the more noticeable the colour – this is particularly important in diamonds which are two carats or greater.  At Le Juelier, all our diamonds have a grading of J and above.             

Diamond Clarity

The vast majority of diamonds have naturally occurring cracks, flaws or inclusions, created during the crystallisation process during which they are formed at extreme temperatures and pressure deep within the earth’s crust.  The internal imperfections in a diamond are called ‘inclusions’, whilst the surface imperfections on a diamond are called ‘blemishes’.  Diamonds with a lot of blemishes or inclusions tend to have less brilliance, as these imperfections interfere with the light’s path.  The clarity of a diamond refers to the amount of flaws present in the stone.  The fewer the flaws, the higher the diamond’s clarity grading will be. 

Nevertheless, a good cutter will try and cut the diamond so that inclusions or blemishes are not visible through the diamond’s table. Therefore, these marks are often undetectable by the naked eye and do not affect the beauty or general appearance of the stone. 

Clarity Grading

Nearly all diamonds sold in the world are graded according to the Gemological Institute of America’s (GIA) clarity grading scale.  This is an 11 point clarity grading scale which classifies a diamond’s clarity based on the number, colour, reflectiveness and position of visible flaws as examined under a 10x magnifying microscope from top to bottom.  The scale ranges from “Flawless” (FL) to “Included” (I1, I2 or I3).  As outlined previously, inclusions or blemishes found on or under a diamond’s table are easier to detect and will lower the clarity grading more than those imperfections located on the sides of a diamond.  At Le Juelier, all our diamonds have a clarity grading of VS1 or above.  Below is an annotated GIA clarity grading scale for your convenience:   

Clarity Diamond Guide Le Juelier

  • Flawless/Internally Flawless (FL, IF): In ‘Flawless’ diamonds, no inclusions or blemishes are visible under a 10x magnification.  ‘Internally Flawless’ have no visible inclusions under 10x magnification.  Extremely rare and astoundingly expensive.
  • Very, Very Slightly Included (VVS1, VVS2)In VVS1 and VVS2 diamonds the inclusions are so slight that a skilled grader would struggle to detect them under a 10x magnification.
  • Very Slightly Included (VS1, VS2): Inclusions can be detected with effort by a skilled grader under a 10x magnification.  However, inclusions are so minor that they often cannot be seen by the naked eye.  Does not affect a diamond’s appearance or beauty. 
  • Slightly Included (SI1, SI2): In SI1 diamonds inclusions and blemishes are often invisible to the naked eye.  In SI2 diamonds, flaws can be detected by the naked eye with very close inspection.
  • Included (I1, I2, I3): Inclusions are obvious under a 10x magnification and are usually obvious to the naked eye. 

Choosing a Clarity Grading

When buying round brilliants, differentiating between an SI1 and VS or above diamond is extremely tough.  An excellent value, diamonds of this clarity are much less expensive than flawless (FL) or internally flawless (IF) diamonds, which are extremely rare and command higher prices.

Frequently, imperfections in diamonds graded slightly included (SI) are invisible to the naked eye, making them an excellent value.

If your budget is tight, it might be possible to purchase a diamond with a visible imperfection, but hide it beneath a ring claw where it will never be seen.

As diamond size increases, the size of its facets also increases. Because facets are essentially windows into a diamond, the importance of purchasing a diamond with a higher clarity grade increases.

Carat Weight

Diamonds and gemstones are weighed using the unit of measurement known as ‘carat’.  One carat is equal to 0.20 grams.  Gemstones are also measured in size (mm). 

 Carat weight diamong guide Le juelier

It is important to note, however, that gemstone size and weight are not necessarily related.  Different gemstones vary distinctly in densities which mean that a one carat diamond will be considerably smaller than a one carat jade. At Le Juelier we recommend not to rely on carat weight when trying to judge the size of a gemstone or a mounted stone.  To gain an accurate understanding of a diamond’s size, consider carat weight with the following characteristics:

  • The diameter of the diamond measured across the top in millimetres; and
  • The diamond’s cut grade

Measuring the diameter across the top of a diamond is crucial, as this is how they are measured once they are set in a ring.  On the other hand, a diamond’s cut grade will indicate whether the diamond has the best proportions to reflect the maximum amount of light (or sparkle).  Good light performance makes the diamond look bigger. Additionally, a poorly cut diamond may “hide” a lot of a diamond’s carat weight in the base of the stone, making the diamond appear smaller than its carat weight might imply.

Choosing a Carat Weight

  • It is always preferable to have a diamond with a lower carat weight but a higher cut grade, as this will make your diamond appear larger than a diamond with a larger carat weight but poor cut. 
  • To choose the best carat weight of a diamond, consider the size of her finger, the size of your setting, and your budget.  The smaller the finger, the larger the diamond will appear.
  • If a large carat weight is important to you but you're working within a strict budget, consider a diamond with a good cut, SI1-SI2 clarity, and an I or J colour grade.
  • Diamond prices jump at the full- and half-carat weights. Diamonds just below these weights cost significantly less, and, because carat weight is distributed across the entirety of the diamond, small size differences are almost impossible to detect.

Diamond Shapes

The vast majority of diamonds used in jewellery are cut in one of ten, round or fancy, shapes which form the global industry’s standard.  Different diamond shapes have different attributes and characteristics which influence the diamond’s quality, however choosing a shape is ultimately about personal taste.  Below is an analysis of each diamond shape we have on sale at Le Juelier.  

Round Brilliant

Round brilliant diamond

More than 75% of all diamonds sold nowadays are round brilliants; they are by far the most common and solicited style for cutting not only diamonds, but all gemstones.  A modern design, the round brilliant is most innovative method of cutting a diamond.  It relies on advanced theories of light behaviour and mathematical equations to create its 58 facets with perfect proportions and symmetry, which in turn optimise the diamond’s light performance.  Therefore, by choosing the superior round brilliant, one can arguably compromise more in terms of colour, cut and clarity.  

Princess Cut

Princess cut diamond

The princess cut is the second most popular diamond shape after the round brilliant.  It is square or rectangular in shape with pointed corners.  A very popular choice for engagement rings as it displays the same high levels of brilliance as round brilliants with a unique design.  The princess cut suits long fingers and is usually featured with triangular gemstones at its sides.  This design is flexible as it can be worked into almost any ring.

It is extremely important to take a princess cut diamond’s dimensions into account.  A princess cut diamond should ideally be perfectly square with a length-to-width ratio of 1:1.05.  If the diamond is rectangular, the length-to-width ratio should not exceed 1:1.10.   


Marquise diamond guide Le Juelier

The shape of a marquise diamond is said to have been inspired by the smile of the Marquise de Pompadour and custom made by Louis XIV of France.  It has an elongated shape with pointed corners, resembling a rugby ball or American football.  Its shape gives the diamond the illusion of greater carat weight, and therefore they greater size.  With great light performance, marquise diamonds look great as a solitaire or set with round or side stones.  The marquise’s length and its lean frame make fingers appear long and slim.  

In terms of dimensions, the ideal marquise should have a length-to-width ratio of 1.75:2.25.

Oval Diamond

Oval diamond guide Le Juelier

The oval diamond is a modification of the round brilliant.  Therefore, both shapes have high and similar light performance (fire and brilliance).  Its unique shape makes this a popular alternative to the round brilliant.  However, like the marquise, the oval diamond’s elongated shape gives the illusion of greater size.

A length-to-width ratio of 1.35:1.50 is considered the industry standard for the classic oval cut.


Diamond Care

Handle all fine jewellery with care as this will not only considerably enhance its appearance but its durability.  To read a specific guide on pearl jewellery care click here.  Adhere to the following recommendations to ensure your jewellery remains beautiful for generations.


Jewellery should always be kept away from abrasive materials and substances that may damage them, such as vinegar, chlorine, ammonia, hairspray and cosmetics.  Make sure to apply any cosmetics or hairspray before putting on your jewellery.  Making sure the settings and clasps are secure will prevent any unnecessary loss.  Use a clean, soft and damp cloth to wipe your jewellery after wearing it in order to remove body oils and dirt before storing them.


Clean and wash your gemstone jewellery frequently will keep it looking brand new.  You can use a simple soap-water solution to soak the majority of non-porous gemstones.  Use a soft toothbrush in order to clean small crevices.  Do not use any rough or metal bristles.  Make sure to dry each item gently with a clean, soft, warm, damp cloth after soaking.  Certain gemstones require special attention and care as they might be sensitive to abrasive substances or even high and low temperatures.  At Le Juelier we implore you take particular care with gemstones such as pearls, coral, lapis lazuli and opal and their surfaces are porous.


In terms of storage, we recommend you keep your items of jewellery separate from each other as this will minimise the risk of the any item getting scratched.  It is best to store your jewellery items individually in a soft pouch.  However, if this is not possible, you can wrap each jewellery item in a soft cloth or linen before storing them in your jewellery box.

Types of diamond setting

Whether it’s an engagement ring and your first-time diamond purchase, or simply a gift for a loved one, we present to you our guide to ring settings, complete with definitions and photos for each term. The stone, metal, and mounting should be chosen with your lifestyle and budget in mind.

Prong Setting

Prong setting diamond guide Le juelier

The most common and classic ring setting is called a prong setting. A prong is a little metal claw that grips the diamond tightly, holding it in place. Prongs can be rounded, pointed, flat, or V-shaped (the latter being the most common for princess-cut diamonds). Most prong settings feature either four or six prongs; with the former you can see more of the diamond, but the latter is more secure. 

If you have a heart-, marquise-, or pear-shaped stone, be sure its points are cradled in a V-shaped prong for protection. Flat prongs are recommended for emerald-cut stones.


  • Permits the most light exposure from all angles and therefore maximizes a diamond's brilliance and "lightens up" richly coloured gems.
  • Less metal means less time and money is required than other setting styles.
  • Allows easy cleaning of the stone.
  • Holds even the most fragile (soft) gems securely.



  •  Offers less protection to the stone than other styles since most of the girdle (the perimeter of the stone) is exposed.
  •  Prongs can snag on clothing or other materials, especially if they are high-set. A lower-set prong setting can be more practical for women with very active lifestyles.


Of the prong settings, the most common is the solitaire setting featuring one diamond or other precious stone. The solitaire setting draws all of our attention to the stone with little to distract us like other stones or fancy metalwork. Another variation of the prong setting is the cathedral setting, an elegant and classic engagement ring settings. Similar to the graceful arches of a cathedral, this ring setting uses arches of metal to hold the diamond or other gemstone.

The cathedral may be set with prongs, bezel, or tension setting since the defining characteristic of this ring is not how the diamond is held but rather how it is mounted with arches above the rest of the shank. The arches can add extra height and make the centre stone appear larger

Pave Setting

Pave setting diamond guide Le juelier

The pavé setting, pronounced “pa-vay,” comes from the French word “to pave,” as in paved with diamonds. By closely setting small diamonds together with minimal visibility of the tiny metal beads or prongs holding the stones in place, the effect is one of continuous sparkle.

The jeweler typically drills holes into the ring, carefully places the diamonds into the holes, and finally forms tiny beads, or mini-prongs, around each diamond to secure them into the holes.

This setting is also known as a bead setting and in the case of especially small stones, may be called a micro-pavé setting. Diamonds are said to be pavé-set when they are as small as .01-.02 carats and any smaller than that would be called micro-pavé.

Pave Setting Benefits

Pavé settings makes the center stone pop and are a great option to give extra sparkle to a lower-set or less sparkly center stone. Just a word of caution: if the ring is pavé set around the entire band, ring sizing can be very difficult.

We recommend confirming ring size early in the design process in order to prevent any problems with fit when the ring is finished.

Channel Setting

Channel setting diamond guide Le juelier

This setting is most frequently used for wedding and anniversary bands or stackable rings that feature only smaller stones and no centre stone. A Channel setting will set the stones right next to each other with no metal separating them. The outer ridge of metal is then worked over the edges of the stones. Keep in mind that round stones cost less to set than square or rectangular ones.


  • Protects the girdle of the stones.
  • Provides better security for small stones than a prong or pave setting.
  • The surface is completely smooth and unobtrusive.


  •  Offers less protection to the stone than other styles since most of the girdle (the perimeter of the stone) is exposed.
  •  Prongs can snag on clothing or other materials, especially if they are high-set. A lower-set prong setting can be more practical for women with very active lifestyles.

Bezel Setting

Bezel setting diamond guide Le juelier

The bezel setting is the second most popular ring setting due to its modern look and suitability for an active lifestyle. Instead of holding the diamond with prongs, the bezel setting encircles the diamond, or centre stone, with a thin metal rim custom-made to hold the stone tightly in place.

A bezel setting can be a full or partial setting: a full bezel completely surrounds the diamond whereas a partial bezel leaves the sides open. 


  • Protects a stone's girdle from being nicked or chipped.
  • Conceals existing nicks or chips on a stone's girdle.
  • Secures a stone well.
  • The ring surface is completely smooth.
  • Metal can be moulded to fit any stone shape snugly.
  • A white metal encircling a white stone can make the stone appear larger.
  • A yellow gold bezel setting can enhance the colour of red or green gemstones.


  • A yellow gold bezel setting can make a "white" stone such as a diamond appear less white because the yellow tint of the setting is reflected in the stone.

Tesion Setting

Tension setting diamond guide Le juelier

The tension setting is named for the tension of the metal band that secures the diamond in place; the result is that the diamond appears suspended between the two sides of the shank.

With the help of lasers used to calibrate the exact dimensions of the diamond, the jeweller expertly cuts tiny grooves into the sides of the band, or shank, so that the diamond, or other precious stone, is literally held by the pressure of the custom-designed metal band pushing into the sides of the stone.

The minimal interference of metal can give the impression that the stone is "floating". 


  • Allows a lot of light into the stone.


  • Ring is built to fit and difficult to resize at a later date.
  • Repair options are limited; only the manufacturer can fix your ring.
  • Less metal means less protection to the girdle of the stone; recommended for less active people or for special occasions only (not everyday wear).
  • Not recommended for gems other than diamonds, sapphires, or rubies.

Flush Setting

Flush setting diamond guide Le juelier

Popular for men's rings, this setting sets the stone "flush" into a hole in the ring so that it does not protrude at all. The ring's metal is then pressed and hammered around the stone's perimeter to secure it.


  • Protects a stone's girdle from being nicked or chipped.
  • Conceals existing nicks or chips on a stone's girdle.
  • Secures a stone well.
  • The ring surface is completely smooth.


  • More time-intensive to set and expensive than a prong setting.
  • Not recommended fragile gems such as esmerald, opals, or tourmalines

Bar Setting

Bar setting diamond guide Le juelier

Setting diamonds separately between vertical bars of metal is another way to set precious stones.

Bar settings are similar to channel settings, but the difference is that channel settings enclose the diamond on all sides whereas the bar setting leaves the diamond exposed on two sides, held in place by the metal bars that secure the stones on the other two sides.

This setting can compliment a centre stone or stand alone for an impressive wedding band or stackable ring. 


  • Protects the sides of each stone's girdle.
  • The surface is relatively smooth and unobtrusive.
  • Puts a contemporary spin on a classic look.


  • Leaves the top and bottom of the stone exposed.
  • The uneven edges of some designs may cause discomfort.

Halo Setting

Halo setting diamond guide Le juelier

The halo setting refers to the placement of diamonds or other gemstones in a concentric circle or square around a centre stone. The halo setting makes the centre stone appear larger — a great option to boost the appearance of a small diamond — and it increases the overall sparkle of the ring.

A halo setting, then, can be a way to save money on a smaller-carat diamond while not sacrificing the overall appearance of the ring. In addition, adding a halo of coloured gemstones or setting the halo diamonds with a different colour metal can make for a contrast in colours.

Cluster Setting

Cluster setting diamond guide Le juelier

A cluster setting “clusters” stones tightly together in order to look like a large diamond. It can either contain a larger centre stone or cluster together stones of equal size.

Side Stone Setting

Side stone setting diamond guide Le juelier

Side stone engagement ring settings consist of a centre diamond that is usually accompanied by two or even more smaller sized diamond next to the centre diamond. The side stones provide more sparkle and brilliance to the overall engagement ring.

Unlike Pavé ring settings or Channel Set ring settings the side diamonds are bigger. One drawback of side stone ring settings is the fact that they distract more from the centre diamond. A side stone ring setting usually comes with a round cut centre diamond or a princess cut centre diamond.

Three-Stone Setting

The three-stone ring setting is a particular variation of the side stone ring setting. It is a versatile setting that can be used for engagement, anniversary, or any occasion. The three stones are said to symbolize the couple’s past, present, and future.

These stones can either be all the same size or, as is often the case, the centre stone is larger than the two side stones. One can personalize this setting with coloured side stones, such as sapphires, rubies, emeralds or other birthstones.