Diamond Basics


Carat Weight

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. Click here for a more detailed explanation.


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. Click here for a more detailed explanation.



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. Click here for a more detailed explanation.



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. Click here for a more detailed explanation.


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.

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 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.

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 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.

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.

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.

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.


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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.


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.

stock available now - view before you buy - come in and visit us - wholesale diamond merchant with over 50 years experience
King St Sydney CBD - by appointment - +61 2 9233 2455 - Copyright 2016 GP Israel Diamonds, Susie Israel - Queen of Diamonds