Diamond Basics

THE FOUR Cs : CARAT

Refers to the standard unit of weight for diamonds and other gemstones. Carat weight is measured using precise electronic scales, rounded to the nearest hundredth of a carat.

THE FOUR Cs : COLOUR

Refers to the colour scale which extends from D (colourless) to Z (light yellow or brown). Colour grades are established by comparing each diamond to a set of master comparison diamonds in a standard lighting and viewing environment. Each letter grade represents a range of colour.

More : The Matter of Size

Carat weight is the only fact of a diamond that can be scientifically measured, everything else is an opinion.

It takes more than 250 tons of ore, blasted, crushed and processed to yield just one carat of rough diamond. And only about one fifth of all rough diamonds are suitable for gem cutting. A carat equals 200 milligrams, or 0.2 grams, and there are 142 carats to an ounce. This has nothing to do with the “Karat” weight of gold, which is actually a measurement of purity rather than weight. In fact, the gemstone “carat” comes from the carob seeds that were used to balance scales in ancient times.

carob
For jeweler purposes, carats are further divided into points. A one-carat stone equals 100 points. So a half carat stone may be referred to as a “50-pointer,” a quarter carat, “25-points,” and so on. Because large diamonds are rare, they generally have a greater value per carat. For example, the price of a two-carat stone will be several times higher, than say, four 50-pointers of equal quality. Likewise, a diamond that hits the one-carat mark will be worth considerably more than a 95-pointer of the same quality.

More : The Matter of Colour

Acting as a prism, a diamond can divide light into a spectrum of colors and reflect this light as colorful flashes called “fire”. Just as when looking through colored glass, color in a diamond will act as a filter, and will diminish the spectrum of color emitted. The less color in a diamond, the more colorful the fire, and the better the color grade.

Colour is critical, but it can also be confusing. Usually, the more colourless a diamond, the greater the value. Depending on its size, one single increase in colour grade could boost its value by thousands of dollars. However when it shows tinges of yellow or brown, the value drops. Yet diamonds in vivid colours (referred to as “fancy”) are prized by collectors.

Diamond colours are graded on a simple system, beginning with ‘D’ for colourless and moving down the alphabet to stones with traces of colour to stones with visible shadings. By the time you reach the second half of the alphabet (M-Z), you’ve found stones with poor colour.

Fluorescence
Fluorescence is a form of lamination created when a diamond is exposed to a low or high wave of ultraviolet radiation. Faint or medium fluorescence rarely affects the diamond’s appearance and it’s usually invisible to the human eye in ordinary light unless the fluorescence is certified Very Strong or Extremely Strong. Diamonds with no fluoresces or faint to moderate fluorescence are preferable. Diamonds with strong fluorescence in colour grades lower than the grade of ‘H’ will often appear much whiter than a nonfluorescent diamond.


THE FOUR Cs : CLARITY

Refers to internal features (inclusions) and surface characteristics (blemishes) within or on a diamond when viewed with 10X magnification under standard viewing conditions. The Clarity Scale includes eleven grades ranging from Flawless to I3.

THE FOUR Cs : CUT

Refers to how the proportions and finish of a diamond affect its overall appearance and quality. Cut is generally graded on a scale from Excellent to Poor and incorporates the diamond’s brightness, fire, scintillation, weight ratio, durability, polish and symmetry.

More : Throwing some light on clarity

What is clarity?
Clarity indicates how “clean” the diamond is, or how many inclusions (i.e. scratches, trace minerals or other tiny characteristics) the diamond has.

Does clarity grade affect a diamond’s sparkle and brilliance?
The clarity grade of SI and better has little effect on a diamond’s visible appearance except in larger diamonds. The larger a diamond is, the larger the facet; larger facets expand the visible clarity. Out of the 4 C’s, clarity is considered the least important. It is primarily the precision of the cut that determines how brilliant and sparkling a diamond will be. The better the cut, the less likely you will be able to see a diamond’s inclusions.

How is clarity grade determined?
The clarity grade is based on the number, size, color, and location of inclusions or blemishes in the stone. The Flawless (FL) grade is given to a stone in which no imperfections can be seen internally (inclusions) or externally (blemishes) when examined with 10x magnification. We recommend that you select an “eye-clean” diamond — one that has no inclusions visible to the unaided eye. An excellent value, diamonds of this clarity are much less expensive than IF- or FL-grade diamonds and typically do not contain visible inclusions that detract from the beauty of the diamond. If you’re considering an SI grade diamond, be aware that some SI2 diamonds will have inclusions that are visible to the naked eye, especially in fancy shapes Pique stones will generally have inclusions that can be seen by the naked eye but are significantly cheaper allowing for a much larger stone for the budget.

More : The Art of Cut

The importance of diamond cut?
While there are many factors to bear in mind when choosing a diamond, diamond cut is probably the most important to consider, as it has a direct correlation to a diamond’s appearance. A well cut diamond with the right proportions will return the maximum amount of light to the viewer’s eye, the diamond will appear more brilliant and beautiful as a result.

How will diamond cut affect a diamond’s appearance?
Diamond cut affects a diamond’s light return properties; also known as scintillation, fire or brilliance. Brilliance refers to the white light that is reflected up through the surface of a diamond, scintillation is the sparkling pattern on a diamond’s surface, and fire describes the flashes of rainbow-colored light which reflect off a well-cut diamond. A well-cut diamond will display brilliance throughout. By contrast, a poorly cut diamond will appear dull or glassy and may have dark areas where light is not optimally returned to the viewer’s eye.

How does cut affect diamond value?
The better cut grades are likely to display more fire and brilliance and since their appearance is more desirable, they are priced accordingly. The cut grade of a diamond also depends on the skill of the diamond cutter. Cutting a diamond with the degree of precision required to produce an ideal cut stone is a rare and valuable skill, therefore diamonds of this grade are more expensive. We recommend selecting a diamond with the highest cut grade your budget will allow in order to maximize the brilliance of the diamond.

What is an Ideal Cut?
Over the years the ‘Ideal Cut ‘ has come in for a lot of discussion, The diagram below illustrates the Ideal Cut but it should be remembered that for Round brilliants there are several so called “optimum” cuts all with slightly different proportions. These are based on scientific formulas to maximize the return of light from the diamond. Ultimately taste and preference for the overall appearance should determine your choice. GP Israel Diamonds – Fantastic prices, great selection, fabulous result! Every proportion and facet in a cut diamond contributes to its optical efficiency. Therefore variations have a direct effect on the beauty of the diamond. If the pavilion is too shallow, light will strike the first pavilion interface within the critical angle, and most light will escape through the pavilion where it will not be seen. This will result in a diamond with considerably less brilliance. It may also show a grey ring and appear dark and lifeless. The trade calls this ‘fish-eye.’ If the pavilion is too deep, light will strike the first interface outside the critical angle and be totally reflected to the other side of the pavilion where it will strike within the critical angle and escape through the side of the pavilion. This will in turn result in a diamond with considerable less brilliance and an obvious dark centre. In the Ideal diamond, most of the light entering through the crown will be totally reflected within the pavilion and will then exit through the crown at an effective angle, resulting in a maximum combination of brilliance and fire.


A FEW WORDS WORTH KNOWING

Buying your diamond is naturally going to involve some discussion. Understanding exactly what some of the more technical terms mean is obviously going to be to your advantage. So here are a couple of definitions and diagrams to help you.

Culet
This is the point on the bottom of the diamond’s pavilion. Although it is often faceted to remove the sharp tip, this facet is usually small and may be quite difficult to see. It is best to select a diamond that has either no culet at all, or at least one that has a very small culet.

Depth
Depth is vital in achieving a diamond’s brilliance and value. When cut to Ideal or near Ideal depth percentages, diamonds display a better-balanced brilliance and thus are worth more. To produce to depth that delivers this extra brilliance, diamond cutters must remove weight from the original rough diamond crystal.

Pavilion
The facets on the bottom of a round brilliant-cut diamond are called pavilion facets. Looking at the diamond face up, these act as mirrors and reflect the image of the table (the large facet on the top of the diamond). This white table reflection indicates how brilliant the diamond will be. In a very fine to Ideal cut diamond, the diamond will exhibit a white table reflection that appears in the centre of the table

Polish
Polish helps light pass through a diamond and so affects its brilliance. You should select diamonds with a polish that is laboratory-certified to be Good, Very Good or Excellent. Diamonds with Poor to Extremely Poor polish are less brilliant because the microscopic polish lines blur the surface and reduce the amount of light that enters or exits the stone.

Symmetry
This is a crucial element in a quality finished diamond. It means the exactness of the shape and the balanced arrangement of the facets. To the unaided eye, finish features usually have little effect on appearance. When selecting your diamond, look for a grading report rating of Excellent, Very Good or Good.

Table
The table is the large flat facet on the top of a diamond. It directly affects the sparkle. The size of the table, along with the angle of the crown is responsible for the balance between brilliance (the flashes of white light bouncing back to the eye from within the diamond) and the play of colours created by refracting light as it prisms its way through a diamond’s facets.

Girdle
The girdle is the outer edge of a diamond. Its grade is determined by its appearance at its thinnest point and thickest point. It can be faceted, polished smooth, or have a slightly granular appearance. Very fine cut diamonds often have faceted girdles. To carefully facet a girdle’s edge takes the cutter more time but a faceted girdle does not improve the diamond’s grade. Most labs grade only the thickness of the girdle and not the surface appearance.

girdle

SHAPE

The other aspect to the cut of the diamond refers to the various shapes available.
Since all diamond shapes are very different, unique characteristics determine quality for each shape.

Diamond-Shapes-pic

Round
The round brilliant cut diamond is by far the most popular and most researched diamond shape available today. For many years, diamond cutters have been using advanced theories of light behavior and precise mathematical calculations to optimize the fire and brilliance in a round diamond. In addition a round diamond will typically give you more flexibility in terms of balancing cut, color, and clarity grades while still getting the fire and brilliance you want.

Princess
This is today the most popular non-round diamond. Its beautiful brilliance and unique cut makes it a favorite. The princess cut has pointed corners and is traditionally square in shape, however can also be rectangular.. Also, princess-cut diamonds can vary greatly in how square or rectangular they are. All things being equal a Princess Cut will be cheaper than a round brilliant cut.

Emerald
What makes this shape different is its pavilion, which is cut with rectangular facets to create a unique optical appearance. Due to its larger, open table, this shape highlights the clarity of a diamond and inclusions may be more visible.

Also, emerald-cut diamonds can vary greatly in how rectangular they are and this is really a matter of personal choice. If in fact you prefer an emerald cut with a squared outline, look for an Asscher-cut diamond.

Asscher
This beautifully unique shape is nearly identical to the emerald-cut, except that it is square. Also, this shape has a pavilion that is cut with rectangular facets in the same style as the emerald-cut.

Marquise
The shape of a marquise diamond can maximize carat weight, giving you a much larger-looking diamond. This brilliant-cut diamond looks beautiful set with round or pear-shaped side stones, and the length of the marquise makes fingers appear long and slender. Again the dimension of marquise you want should be a personal choice however for the most traditional marquise-cut diamonds, look for length-to-width ratios between 1.75 and 2.25

Oval
An oval diamond has beautiful brilliance that’s similar to a round diamond. Oval diamonds are also very popular as their length can accentuate long, slender fingers. The length-to-width ratio will determine the diamond’s outline, or what it will look like when viewed from the top.For the most traditional oval diamonds, look for length-to-width ratios between 1.30 and 1.66.

Radiant
Trimmed corners are the signature of this diamond, and they help make the radiant-cut a popular and versatile choice for jewelry. A radiant-cut looks equally beautiful set with either baguette or round side-diamonds. Radiant-cut diamonds can vary in their degree of rectangularity. For a radiant diamond shape that is square, look for length-to-width ratios between 1 and 1.05. If you prefer more of a rectangular shape, look for length-to-width ratios greater than 1.10.

Pear
This brilliant-cut diamond is also called a teardrop for its single point and rounded end. The unique look of the pear shape helps make it a popular choice for a variety of diamond jewelry. If you choose an elongated pear shape, the length of the diamond creates a subtle slimming effect on the fingers.

Heart
The heart is the ultimate symbol of love. The unique look of the heart-shaped diamond helps make it a distinctive choice for a variety of diamond jewelry. For a more traditional heart-shaped diamond, look for length-to-width ratios between .90 and 1.10.

Cushion
This unique shape has been popular for more than a century. Cushion-cut diamonds (also known as “pillow-cut” diamonds) have rounded corners and larger facets to increase their brilliance. Cushion-cut diamonds are available in shapes ranging from square to rectangular. For a cushion-cut diamond that is square, look for length-to-width ratios between 1 and 1.05. If you prefer more of a rectangular shape, look for length-to-width ratios greater than 1.15.

CERTIFICATION
Before purchasing a diamond, you should expect to review a copy of its certificate as proof that it has undergone an unbiased, professional examination.Virtually all our stones above 0.50cts of SI2 clarity and better, I colour and better come with an independent and professional grading report.A diamond certificate, also called a diamond grading report, diamond dossier®, or diamond quality document, is a report created by a team of gemologists. The diamond is evaluated, measured, and scrutinized using trained eyes, a jeweler’s loupe, a microscope, and other industry tools. A completed certificate includes an analysis of the diamond’s dimensions, clarity, color, polish, symmetry, and other characteristics. Many round diamonds will also include a cut grade on the report.There are many laboratories issuing diamond grading reports, some reputable and reliable and others not so. The reputable laboratories we use are

  1. GIA     – Gemmological Institute of America
  2. HRD    – Hoge Raad Voor Diamant, Diamond High Council – Antwerp Belgium
  3. DCLA  – Diamond Certification Laboratory of Australia
  4. GSL    – Gem Studies Laboratory of Australia

Please be aware that stones with certificates from EGL & IGI are not comparable to the abovementioned laboratories’. EGL & IGI tend to over grade diamonds and have much less strict grading scales.

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