Know Your Cuts of Diamond!

This article is for anyone looking forward to purchasing a diamond ring (and for brides who anticipate having some input into that selection).  Armed with this important knowledge, you’ll have much more confidence when making this major purchase.

Keep in mind that this article refers to natural diamonds since the process of diamond formation is now being replicated by artificial means. Let’s begin our diamond travels with composition.

Know Your Diamond Composition

Diamonds are formed in high temperature conditions in the earth’s core with a ‘growth’ period of between 1 billion to 3.3 billion years. Diamonds are brought to the surface by volcanic eruption where magma cools into igneous rock. These diamonds develop over several stages and are thus prone to imperfections. The hardest diamonds, found in Australia, have only a single growth stage and therefore develop into some of the purest diamonds on earth. (Diamonds can also be grown by chemical vapour deposition, a human-made technique which tries to mimic natural processes).

Diamond is a transparent crystal, a mineral. It is one of three existing forms of carbon, the others being graphite and fullerene. Diamond is the hardest known natural mineral, but this hardness depends on purity and crystal orientation. Diamonds are comprised of four triangular faces, three of which meet at a point forming a pyramid shape. This configuration forms a very stable chemical bonding contributing to hardness and, in turn, resistance to impurities. Eighty percent of mined diamonds, referred to as bort, are used for industrial purposes such as abrasives, drill bits, and polishing; for such diamonds, clarity and colour are not an issue.

Faultless Diamond

Most diamonds contain some form of impurity. Impurities arise from chemical composition, structural defects, or a combination thereof. Chemical impurities, which introduces colour into the otherwise colourless diamond, can either enhance or detract from the gem’s value.  Let’s look at the issue of impurity and colour in more detail.

Yellow Diamonds

Nitrogen is the most common impurity in diamonds. Diamonds with nitrogen impurities are referred to as Type I diamonds and are mostly mined in South Africa. The configuration of the nitrogen atoms produces two different outcomes. The first and most common result of nitrogen is only a slight change in colour.

Non-fancy low saturation, pale yellow diamonds are graded as ‘normal’ white diamonds. These are considered to be less desirable than colourless and near-colourless white diamonds. Diamonds that are graded as ‘fancy’ (from light yellow to deep yellow) are often called ‘canary’ diamonds and are much sought after. Fancy intense yellow and fancy vivid yellow diamonds are rare, expensive, and desirable. Collectors look for the fancy yellow deep hues. Yellow diamonds are the second most common type of diamond after white diamonds.

Boron is another impurity. Diamonds containing boron are blue to grey in colour. The blue occurs as a result of the penetration of red and infrared light during formation. These are classified as Type IIb diamonds. (Diamonds can be ‘treated’ to look blue as well). Natural blue stones are so rare that most jewelers never see one.  Blue stones are more prestigious than yellow diamonds. Think Hope Diamond and the Royals (photo right).

Radiation or alpha particles are known to cause green diamonds. Intense brown, pink, or red diamonds are the result of a structural deformation of the crystal. (Classified as TypeIIa diamonds). Red is the rarest of all diamond colours and is produced from mines in Australia.  Again, most jewelers never see a natural red diamond although many red artificially produced diamonds are common in the marketplace.

Know Your 4 C’s: Cut, Colour, Clarity, Carat

Cut does not refer to shape per se, but rather to the symmetry of facets (the flat angled faces) on the face or crown. The way facets are arranged determines the extent to which the diamond will sparkle when moved. Sparkle, or brilliance, is also determined by the size, number, and symmetry of facets and quality of polish. Small stones will appear dull if there are too many facets; so will large stones if the facets are too large and too few. The crown of a diamond is like a prism and high quality diamonds refract light broadly like a fan, known as a diamond’s fire. A good diamond also has high dispersion power which is how the refracted light splits into a rainbow or spectral colours. A good cut permits the maximum amount of light to be reflected through the gem creating maximum fire, brilliance, and dispersion, all of which are graded.

Colour is another characteristic by which diamonds are graded. Normal colour range diamonds are rated on a scale from D-Z. Due to flaws, most diamonds are tinged with varying degrees of yellow. Only D-F classified diamonds have the ‘icy’ look. Diamonds over Z fall into the fancy category and are graded on the same scale as emeralds, rubies, and sapphires.

As we can see by the diamond comparison to the left there is a significant difference between colourless and light yellow diamonds.  The difference between the colourless and near colourless is a slight tinge of yellow, grey, or brown that is only detectable under 10x magnification. The lower down the scale the more observable the colour.

Clarity refers to visual appearance of the diamond. Clarity is graded in terms of surface appearance and internal structure. Surface wise, a diamond may have blemishes such as pits, nicks, chips, lines, or scratches.  Some of these blemishes occur during the cutting and polishing process. Internal or structural imperfections such as cracks or foreign matter interfere with the refraction of light resulting in a milky or dull look. The grading scale ranges from FL (Flawless) to I (Included).  The term ‘Included’ refers to surface and structural imperfections seen under 10x magnification. Ask your jeweler to show you where your choices fall on the clarity grading scale.

A carat is a unit of weight  for gems, not to be confused with karat which refers to gold quality. A carat is equal to 200 mg or 0.007055 oz. A ‘paragon’ is a flawless diamond of at least 100 carats (.20 grams). Prices for diamonds are expressed as price per carat. The more a diamond weighs, the more each carat will cost. For example, in comparing two diamonds with the same characteristics, the two carat diamond would be priced at $55,000.00 whereas a four carat diamond would be priced at $286,500.00. The weightier the stone, the more the price exceeds the price per carat. Since it is more profitable to divide average or poor stones into smaller diamonds, usually only first quality stones end up as large gemstones.

Know Your Shapes of Diamond

Now that we have examined the four C’s, let’s look at some popular diamond shapes. As we now know, most consumers associate shape with cut. Although shape is an outcome of cut, cut is largely determined by the initial shape of the stone, the location of flaws, carat weight, as well as consumer demand.

Round Brilliant Cut is the most common shape given to diamonds. It usually has a 58-facet form and is considered a ’safe shape,’ therefore making it a popular choice for grooms. Heart and Arrows is a much sought after pattern in brilliant-cut diamonds (see photo). Looking down through the crown, the pattern appears as a series of eight arrowheads. Viewed from underneath or from the ‘pavilion,’ the pattern appears as eight heart shapes. Hearts and Arrows patterns are graded, with the best revealing superior symmetry and optimal facet placement. Depending on quality, H&A patterned diamonds are priced at a premium.

Cuts other than round brilliant are referred to as ‘fancy cut.’ Fancy cuts can be grouped into four categories: modified brilliants, step cuts, mixed cuts, and rose cuts. Let’s take a look at each in turn.

Modified Brilliants are brilliants in a wide range of shapes, like Marquise, Heart, Oval, Pear, triangular Trillion, and drop cuts. Like the Round Brilliant, they usually have 56 facets.

Step-Cut diamonds are stones that are square, rectangular, triangular, and trapezoid. The name Step-Cut is derived from the step-like shape. On the square and rectangular shapes the corners are often slightly rounded to avoid damage (See Asscher & Emerald cut). Because the crown and pavilion are shallow, step-cut stones are not as bright as brilliants. They do, however, accentuate whiteness, luster, and clarity since the slightest flaw is visible in the flat crown.

Mixed Cuts share the optical characteristics of the modified brilliant cut and the weight and dimensions of step-cuts. Princess, Radiant, and Flanders cuts are popular mixed cut diamond shapes.

Princess Cut Diamond

Princess cut diamonds, a mixed cut first introduced in 1960, have become so popular they have their own stringent grading standards. The Princess 144 has 144 facets. Quality Princess cut diamonds have higher fire and brilliance than other mixed cut diamonds and waste the least original crystal. (Up to 50% of diamond is usually sheared off in the cutting process).

Rose Cut Diamond

Rose cut diamonds have a flat base and a crown composed of 12-24 triangular facets. Fashionable in the last century, they are usually now only antiques.

Wedding Magazine hopes this brief tour of the world of diamonds will help prepare you when it comes time to purchase your wedding rings. Look for Wedding Magazine’s & Ella Bella Photographic’s upcoming interview with a leading Vancouver jeweler who will take us through the purchasing process.