Diamond Selection


Diamond selection parameters

Selection of a diamond is based on the famous 4C's of the diamond. Let us find in detail that what these 4C's stand for and what are basic selection technique for diamond.

Diamond basic attributes – the 4Cs

  1. Cut of the diamond
  2. Colour of the diamond
  3. Clarity of the diamond
  4. Carat of the diamond

Cut

The beauty of a diamond depends more on cut than any other factor. While all the other Cs are largely determined by Nature, cut is the one that can be determined by Man. For this reason, cut is perhaps the most important of the four Cs for us to understand.

Cut refers to the proportions, polish, and symmetry of a stone: these three factors are important in creating a diamond with the best possible light reflection. The angles and finish of any diamond are what determine its ability to handle light, and its brilliance.

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, and it's this sparkling blaze that makes diamonds so captivating.

A poor cut, on the other hand, can cause light to seep out of the sides and bottom of the diamond, or it can limit the amount of light that enters a diamond. Poor cuts can therefore cause the diamond to appear dark, dull and lifeless, despite its colour and clarity grades. This is why cut is the most significant factor in the appearance of a diamond.

Brilliance, Fire and Scintillation

The cut of a diamond has three primary effects on appearance: Brilliance, Scintillation, and Fire.

Brilliance refers to the brightness of a diamond, created by the combination of all the white light reflections from the surface and the inside of a polished diamond. When light hits a diamond's surface, some light enters and some is reflected back. The amount of light immediately reflected back depends upon the crown's angles.

The cut of a diamond also creates “contrast”, the light and dark areas seen in a diamond. These dark areas are not inclusions, but shadows created by the cut or by objects between the light source and the diamond (such as the observer's head).

The greater the amount of reflected light and the stronger the contrasts, the more brilliant the stone. A round diamond will typically exhibit more brilliance than a fancy shape due to the superior mechanics of the round cut for reflecting light.

Scintillation refers to the flashes of light, or sparkles, which are produced when a diamond is tilted from side to side. These flashes are caused when light that isn't immediately reflected back enters the diamond and bounces off the internal walls. They are most pronounced in flood lit areas where strong light enters the diamond from multiple angles.

The light that reflects out of a diamond can appear in brilliant white flashes, or in a rainbow of colour, referred to as Fire. The fire effect is caused by the proper bending and dispersion of light as it travels through the diamond. The more colourless the diamond, the truer the dispersed colours will appear.  This effect is greater in darker areas where there are fewer light sources.

Maximum brilliance is achieved in diamonds that posses both greatest fire and best scintillation.

Understanding Diamond Anatomy

To properly understand a diamond's cut, it is important to understand the terminology of basic diamond structure as it relates to proportion, symmetry and polish.   

Diameter: The diameter is the width of a polished diamond from one side of the girdle to another  

Table: The table is the largest polished facet of the diamond on the top face of the stone

Crown: The crown is the top part of the diamond that is measured from the surface of the table to the girdle

Girdle: The girdle is the widest edge of the diamond where the crown ends and meets the pavilion

Pavilion: The pavilion is the bottom part of the diamond that begins at the girdle and extends downward to the point of the culet

Culet: The culet is the tiny flat facet at the bottom tip of the diamond

Depth: The depth of a diamond refers to the total length of a diamond, measured from the culet to the table

 


Proportion, Symmetry and Polish

  • Diamond Proportion

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.

To optimally capture light and reflect it back, a diamond's pavilion must have accurate angles and depth. If the angle of the pavilion is too shallow or too deep, light will escape or leak out, creating dark and dull "stains". The crown angle is also extremely important since this affects the way that light enters and exits the diamond.

Not only are the angles important, but depth percentage and table percentage are also key factors that contribute to the quality of a diamond's cut. Depth percentage refers to the depth of the diamond divided by its diameter. Shallower diamonds have low depth percentages whereas deeper diamonds have higher depth percentages. A good target depth percentage for a round diamond is considered to fall between 59 and 62.5%. Table percentage refers to the width of the table divided by the diameter. Again, diamonds with a higher table percentage have larger tables, and diamonds with a smaller table percentage have smaller tables. A good target depth percentage for a round diamond is considered to fall between 53 and 59%.

  • Diamond Symmetry

A diamond's facets must be symmetrical in order to maximize the amount of light that enters and exits the stone. Diamonds with poor symmetry look slightly distorted, unbalanced and improperly shaped. Moreover, they will affect brilliance, scintillation and fire. Many asymmetrical round stones are not completely round, or have misshapen facets or off-centre culets.

  • Diamond Polish

Once a diamond is cut, each facet of the diamond is polished. If the polishing is done improperly, it can leave scratches and streaks that are similar to the marks left behind after a car waxing. An Excellent diamond polish is a diamond which has very few or no scratches.

Cut Grades

Ideal/ Excellent – Excellent light performance. Reflects almost all of the light that enters. Rare and extremely beautiful cuts.

Very Good – Very good light performance. Reflects almost all of the light that enters. Very Good diamond cuts are considered to be an outstanding value.

Good – Good light performance. Reflects most of the light that enters. Good diamond cuts are far less pricey than Very Good cuts.

Fair – Not as brilliant as a Good cuts or above, Fair diamond cuts are still considered good quality diamonds.

Poor – Poor cut diamonds are typically cut too shallow or too deep causing much of the light to leak out of the diamond's sides and base.


Which Grade of Cut Should I Buy? 

Cut grade is the most important factor in determining the overall appearance of a diamond, because a poorly cut diamond will seem dull even with excellent clarity and colour. Conversely, a well cut diamond can have a slightly lower colour (G-H) or clarity (SI1-SI2) and still look quite beautiful, due to its superior ability to create sparkle and brilliance.

For superior brilliance, choose a diamond with a Cut grade of Very Good or Excellent for round diamonds, and Good or better in fancy shape diamonds. When choosing a diamond in this range, make sure its Symmetry and Polish are Very Good or Excellent, so that the impact of the above average Cut is not obscured.

For those on a budget, primarily concerned with size, a diamond of Fair - Good cut may be an acceptable choice, especially in fancy shapes. While the diamond will lack the scintillation and brilliance of a well cut diamond, it will allow a significant increase in size for the same price.

Avoid Poor cut diamonds, even if size is the primary concern. Most find these diamonds to be an unacceptable trade off, despite the lower price.

The number one mistake made when purchasing a diamond is to be misled on cut quality. Cut is more difficult to define than color or clarity, and therefore often ignored or misrepresented. Common issues include:

  • Being shown two or three diamonds of various cut qualities, in an effort to sell the best of the available options. While the customer may choose the best option shown, it is not necessarily a well cut diamond. It is simply the best of what is currently available at that particular store.
  • Purchasing a deeply cut diamond. A deeply cut diamond carries more of its carat weight "hidden" in the depth of the diamond as opposed to the width. These poorly cut diamonds are less expensive per carat, and are common in most jewelry stores. A customer might purchase a 1.00 carat diamond that actually looks like a .90 carat diamond because it is too deeply cut.
  • Because well cut diamonds are more expensive per carat than fair or good cuts, few are carried in traditional jewelry stores. Less than well cut diamonds cost less to purchase, less to inventory, can be sold at a lower price, and turn more quickly in the jeweler's inventory - so the incentive to carry them is overwhelming.

Tips

  • A diamond’s "cut" is different from its "shape." “Shape” refers to the general outward appearance of the diamond, (such as round, emerald, or pear). "Cut” is a reference to its reflective qualities.
  • If you opt to buy a diamond without a 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").
  • Remember that observable fire is increased in a slightly darker room (such as a candle light). Conversely, scintillation is maximized in strongly lit areas (such as an office). Fire and scintillation are simultaneously maximized by very strong, pinpointed light sources (such as the spot lights prevalent in jewellery showrooms).
  • Unlike the other "Cs" (carat weight, colour, and clarity), the various Cut grades in existence today were not originated by GIA, and are not uniformly applied. In fact, GIA has only been assigning cut grades since 2005, and only to round diamonds. Even though retailers use common terms to describe Cut (such as Excellent, Very Good, Fair, Poor) the terms are not uniformly defined or applied. In fact, a diamond seller may assign any cut grade they choose, based on any set of factors they wish.

 

COLOUR

When we speak of Colour in a diamond, we actually mean the degree of colourlessness. While most diamonds are white, not all are truly colourless. Many are tinted yellow to brown or silver to grey.

In a white diamond, the presence of a tint is considered undesirable. This colour impurity is caused by lingering traces of nitrogen, boron, hydrogen or other elements. Commonly, diamonds are affected solely by nitrogen traces, which create pale yellowish or brownish tints. Only diamonds composed of 100% pure carbon without any impurities may be completely colourless.

Diamonds are graded on a Whiteness scale or absence of colour scale. Basically, the whiter or clearer the colour of a diamond the greater its value.

 

Grading

The Gemological Institute of America (GIA) has devised a set of guidelines to grade diamond colour. The colour of graded diamonds is compared to that of control stones, which are preselected gems of a specific colour.

To be graded, diamonds must be loose stones, because once a diamond is set into metal the metal can affect its colour. Diamonds are placed table-down, pavilion-up and viewed with a 10X loupe under controlled lighting and precise viewing conditions. A lettering system from D to Z is used to identify the amount of colour present in each diamond, with D awarded only to rare, totally colourless diamonds. Many of these colour distinctions are so subtle that they are invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.

 

S. No

Colour

Description

Book My jewellery’s selection

1

D

Absolutely colourless. The highest colour grade, which is extremely rare.

 

 

 

Recommended and used in entire range on www.bookmyjewellery.com

2

E

Colourless. Very negligible traces of colour can be noticed by an expert gemmologist. A rare diamond.

3

F

Colourless. Very negligible colour traces can be seen by an expert gemmologist, but still considered a "colourless" grade. A high-quality diamond.

4

G-H

Near-colourless. Colour noticeable when compared to diamonds of better grades, but these grades offer excellent value.

5

I-J,

Colour slightly detectable. An excellent value.

6

K-M

Noticeable colour.

Neither recommended nor used in any of the product at www.bookmyjewellery.com

7

N-Z

Noticeable colour.

 

 

 

Fancy Coloured Diamonds

A few diamonds are exceptions and do not fall into the colour category set by GIA. They are referred to as the fancy coloured diamonds. The well-defined colours include pink, canary yellow, blue and green. Some are quite rare and hence expensive.

In a fancy colour diamond, intensity and hue of colour plays the most important role in deciding value. If a diamond has very intense colour and is rarely found, it can even be more expensive than colourless or white diamond.

Fancy yellow or brown diamonds are commonly available, so they are priced relatively less than colourless diamonds. On the other hand, pink, red, blue and green are very rare, and are valued more than colourless diamonds.

The intensity grading system for fancy colour diamonds differs than that of white diamonds. Unlike white diamonds, which range from the letter D-Z, fancy colour diamonds are graded by Light, Fancy Light, Fancy, Fancy Intense, Fancy Deep, Fancy Dark, and Fancy Vivid.

Fluorescence

Fluorescence is another factor that can affect diamond colour.

This is an effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light (such as the lighting frequently seen in dance clubs). Under most lighting conditions, this fluorescence is not detectable to the eye. Since UV radiation is a component of daylight and is also present in fluorescent lit rooms, diamonds with this characteristic can appear to change colour quite often. While most gemologists prefer diamonds without this effect, some people enjoy it. It's really just a matter of aesthetics.

Strong blue fluorescence can make a yellow coloured diamond appear more white, but in rare cases can cause a stone to appear milky or oily. This milky or oily effect is called an "over blue" and only applies to a small number of "strong" and "very strong" fluorescent stones. Stones that fluoresce yellow appear even more yellow under some lighting conditions.


It is common to find that diamonds with colourless grades (D-E-F) or near colourless 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 non-fluorescence.

What Colour Diamond Should I Choose?

The difference in appearance between colourless diamonds and near colourless diamonds may not be detectable, but the price difference from one colour grade to another can be significant. The purists at heart will always demand diamonds in the D-F range. By selecting diamonds in the G-I range, however, you can find a tremendous value while still achieving a "colourless" look.  

If you find that you are sensitive to low colour grades, then we suggest you choose a diamond with the colour grade that satisfies you. However, if you have difficulty differentiating between different colour grades, then you may want to consider a nearly colourless diamond.

Some experts suggest getting a diamond that has a small amount of colour, which will soften the light and make it easier to view the entire spectrum of colour that is given off when the diamond scintillates.

If you are looking for a round brilliant diamond, you have a bit more flexibility in your colour grade, because the brilliance makes it more difficult to detect colour. In this instance, anything over I colour is usually more than adequate, and will appear completely colourless to the untrained eye unless held up against a diamond that is at least 3 colour grades above it, such as an F or E colour diamond.

Diamonds with pointed ends, specifically marquis, radiants, trillion, pear and sometimes even princess shaped diamonds tend to focus the colour on these points. In this case, it is usually best to stay with a colour grade of H and higher. However, if you have a pronged setting, the prongs will usually hide this colour concentration

In addition, when you are looking for multiple stones, such as loose diamonds for a 3-stone ring, it is important to make sure that the colour ranges are at least within 1 grade of each other.

If you are shopping on a budget or trying to maximize the size of your stone, then "J" diamonds are most affordable and still near colourless. You may also want to consider choosing a diamond with medium or strong fluorescence. Since these diamonds are discounted slightly in price you can often afford a higher colour stone without paying the premium.

Tips

  • As diamond size increases, colour becomes more noticeable. This is especially important to keep in mind if purchasing a diamond of two carats or greater.
  • The visible difference between diamonds of one colour grade, for example G to H or I to J, is so minor it is difficult to detect with the unaided eye. The cost savings, however, can be significant.
  • Diamond shapes that reflect more light (i.e. have more sparkle), such as round or princess, can mask some colour in a diamond.
  • The type of metal in which a diamond is set can complement its colour. Consider setting diamonds graded I or J in yellow gold. White gold or platinum best complement diamonds with a colour grade of D to H.

 

CLARITY

Clarity, or purity, is a diamond’s ability to let in light and reflect its brilliance. Of the Four Cs, Clarity is the easiest for you to evaluate and the most straightforward to understand.

We measure the clarity of a diamond by its size and the number of inclusions and blemishes in or on it. Inclusions are interior irregularities and blemishes are exterior irregularities. These imperfections are not flaws, but rather the natural fingerprint of every diamond. Often, we can see these only under a powerful microscope or jeweller’s loupe, and they do not visibly affect the appearance or beauty of a diamond.

Inclusions are flaws such as air bubbles, cracks, and non-diamond minerals found within the diamond, which are caused deep within the earth during its formation.

Large inclusions interfere with the dispersion of light and diminish the diamond's brilliance. They also affect the durability of the diamond, reducing its resistance to fracture. Some inclusions are coloured and also influence the appearance of a diamond.

The larger or more numerous the inclusions the less valuable the diamond.

Blemishes are imperfections on a diamond’s exterior surface and include scratches, pits and chips. Some blemishes such as nicks, pits, trigons, and polishing lines—are a result of the cutting and polishing process. Depending on their location and size, most blemishes can be polished away, or the diamond can be re-cut to eliminate them.

Surface blemishes can affect a diamond’s clarity and value, but many blemishes have little or no impact on a diamond's appearance.

Blemishes typically have less impact on a diamond's value, beauty and grade since they rarely affect the strength and structure of the diamond.

Clarity Grading

Gemmologists’ grade the clarity of a diamond by examining it top-down with a 10x magnifying microscope. Imperfections located on or beneath the table of the diamond are easier to detect and affect clarity grade more than those located around the sides of the diamond. Larger marks, darker marks and deep marks will also significantly affect the clarity of the diamond.   

The Gemological Institute of America's (GIA) International Diamond Grading System™ is the globally recognized standard for diamond clarity assessment. With 11 grades, the system classifies a diamond's clarity based on the nature, position and size of its inclusions and exclusions. The list below summarizes the GIA's International Diamond Grading System.

  • FL Flawless: Flawless diamonds have no inclusions or blemishes detectable under 10x magnification, and are extremely rare.
  • IF Internally Flawless: Internally flawless diamonds have no detectable inclusions but some surface blemishes under 10x magnification, and are rare and very valuable.
  • VVS1/VVS2 Very Very Slightly Included: Inclusions and blemishes are extremely difficult for a even a skilled grader to detect under 10x magnification
  • VS1/VS2 Very Slightly Included: Inclusions and blemishes are detectable under 10x magnification, but are minor flaws that do not impact the diamond's beauty and are frequently invisible to the naked eye.
  • SI1/SI2 Slightly Included: Inclusions and blemishes are easily noticeable under 10x magnification and may also be visible to the naked eye.
  • I1, I2, I3 Included: Inclusions and blemishes are obvious under 10x magnification and typically visible to the naked eye. These flaws may negatively impact the transparency and or brilliance of the diamond.

 

What Clarity Grade Should I Choose?

CaratLane suggests that you work within your budget to select a diamond with the least amount of inclusions and blemishes, qualities which will negatively impact the value and durability of your diamond.

Diamonds with the least amount of flaws hold the highest clarity grading. Flawless diamonds are extremely rare and considered to be the most beautiful of all diamond grades. Because they are so scarce diamond experts consider Internally Flawless diamonds (IF) to be the most valuable examples of near-perfection in the international diamond market.

Many diamond purists insist on FL or IF diamonds, believing that these diamonds are 100% flawless; however, it is important to note that this is not the case. Almost all diamonds have some flaws. FL and IF diamonds simply have no flaws detectable under 10x magnification.

While FL/IF diamonds are the rarest, a diamond does not have to be graded so to be stunning. An "eye-clean" diamond - one that has no imperfections visible to the unaided eye – is an excellent value. SI and VS diamonds are typically considered clarity grades of fantastic value since their inclusions are minor and invisible to the unaided eye.

When looking at diamonds with many facets and a highly brilliant cut, such as round brilliants, there is absolutely no visible difference between a stone that is graded flawless and one graded SI, even though the SI is 7 grades lower. It is much less rare, but no less beautiful.

Fancy shaped and step cut diamonds, such as Emerald or Asscher, are designed with fewer facets and larger tables that emphasize transparency over sparkle, and inclusions in them are easier to detect with the naked eye. Therefore, we recommend choosing a fancy shaped diamond with a clarity grade no lower than VS2.

As diamond size increases, the size of the facets also increases. Because facets are essentially windows into a diamond, the importance of purchasing a diamond with a higher clarity grade increases. For diamonds over 2 carats, a clarity grade of VS2 or higher is the safest bet for avoiding any signs of visible inclusions. In diamonds between 1 and 2 carats, clarity grades of SI1 or better will not have inclusions easily visible to the naked eye.

Tips

  • In diamonds under 1 carat, clarity should be considered the least important of the traditional 4 Cs. You can opt for a lower clarity range in exchange for a higher cut or colour grade.
  • If you cannot tolerate imperfections, even those you cannot see, choose a VVS2 or better diamond. About 10% of all diamonds sold fall into this category.
  • If, while shopping for a diamond, you are ever given a clarity range (e.g. SI1-SI2) as opposed to a specific grade, the diamond is not certified by GIA. The seller is only estimating the diamond's clarity using GIA terminology.
  • If your budget is tight, it might be possible to purchase a diamond with a visible imperfection, but hide it beneath prongs or bezels where it will not be seen. 
  • If you intend to wear the diamond on a regular basis, it is not advisable to wear FL or IF diamonds, as continuous wear and tear will reduce the clarity of these diamonds.
  • Watch out for clarity enhancement techniques such as fracture filling and laser drills, which are used to lessen the impact of inclusions.

 

CARAT

Carat-Weight

A carat is the unit of weight by which a gemstone is measured. The carat-weight of a diamond is the easiest measurement of the 4C’s to determine. Carat-weight is not a factor which denotes the quality of a diamond, but merely its size by weight.

The word "carat" derives from the carob seeds that people used in ancient times to balance scales. So uniform in shape and weight are these little seeds that even today's sophisticated instruments cannot detect more than three one-thousandths of a difference between them.

"Carat” is not to be confused with "karat," which is used to indicate the purity of gold.

One carat is subdivided into 100 "points". Therefore a diamond measuring 75 points is 3/4 carat in weight, or 0.75ct. There are five carats in a gram.

The size of a diamond is proportional to the carat-weight of a diamond. When rough diamonds are cut and polished into finished diamonds, as much as 2/3 of the total carat-weight may be lost. Since larger rough gems of high quality are found less frequently than smaller rough gems of high quality, a single two carat diamond will be more expensive than 2 one carat diamonds of the same quality. However, two diamonds of equal carat-weight can differ greatly in value due to their cut, color, and clarity. 

Carat-weight by itself will not reflect a diamond’s size. Instead, two other factors must be considered:

  1. Distance across the top of the diamond measured in millimetres

Since a diamond is viewed from top when set into a ring or pendant, it is essential to determine the distance across the top of a diamond.  A deeply cut diamond has a greater proportion of its total weight "hidden" in the depth, resulting in a smaller diameter than a well cut diamond. 

  1. The cut grade of a diamond

The amount of light reflected from a diamond depends on its cut grade. Hence, when a diamond is well cut, maximum light is reflected from the top and makes it appear larger.   It is therefore possible to get a diamond of lower carat but with higher cut grade and vice versa.

NOTE:

Carat is abbreviated to "ct" or "CT" when describing a single stone. "TCW," meaning "total carat weight," is added when jewellery is set with multiple diamonds.

It has to be noted that the carat weight does not refer to exactly one figure. It comprises of stones within a certain weight range. For example:

1 carat - Stones in weight range of 0.95 ct to 1.05 ct

0.75 carat - Stones in weight range of 0.72 ct to 0.76 ct

0.50 carat - Stones in weight range of 0.47 ct to 0.56 ct

0.25 carat - Stones in weight range of 0.23 ct to 0.26 ct

This holds true for all carat weight figures.

What Carat-Weight Is Right For Me?

This question has no direct answer. It really depends. Differences in size are clearly visible even to the untrained eye, and weight clearly does matter because it influences cost significantly.

However, size alone does not guarantee beauty.  The quality of a diamond in cut, grade, and diameter should also be considered.

In deciding the importance of carat weight, it is vital to take into account the recipient's preferences.  If the dream is a one carat diamond, even the most beautiful half carat stone will be a disappointment. If a large carat weight is an important factor, but there is a strict budget, consider a diamond with a good cut, SI1-SI2 clarity, and an I or J colour grade.  This will make room for a higher carat weight.

If quality is the primary factor, once the cut, colour, and clarity grade have been selected, it is easy to determine the carat-weight of the diamond that will fit within your budget.

Tips

  • 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 visually.
  • Remember that slender fingers make small diamonds look bigger.
  • Think about what sort of setting will hold the diamond. The setting you choose must be able to fit the carat-weight of your diamond.

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