Diamond Knowledge

Like many precious goods, a diamond's weight bears heavily on its value. Diamond weight is measured in carats: one carat equals 0.2 grams and is further divided into 100 points, so a 50-point diamond equals 0.50 carats. Because even a tiny variance can create a significant difference in cost, diamonds must be weighed with great precision — a diamond is first weighed to the nearest thousandth of a carat, then rounded to the nearest hundredth.

The Relationship Between Weight and Value

Generally, a larger diamond is worth more than a smaller one, but there are exceptions. This is because a diamond's value also depends on the other 4C standards — colour, clarity and cut. For example, a 0.75-carat diamond of D colour and IF (internally flawless) clarity may be worth considerably more than a 1.02-carat diamond of H colour and SI2 (slightly included) clarity, simply because D-colour, IF-clarity diamonds are exceptionally rare.

Certain weights are regarded as 'magic weights' — such as 0.50ct, 0.70ct, 0.90ct and 1.00 carat — because diamonds at these exact weights command a much higher price than those just below them. For instance, a 1.00-carat diamond of D colour and IF clarity with excellent cut, polish and symmetry will be priced far higher than an otherwise identical 0.99-carat diamond.

How to Choose the Right Carat Weight

If you are purchasing a diamond for investment purposes, consider a round brilliant diamond weighing between 1 and 3 carats, in D to G colour.

If you have set a budget, or your budget is a little tight, consider a diamond just below one of these 'magic' weights — it will appear almost the same size as your ideal choice, while allowing the other three C's to remain at a good standard.

Diamond colour grades run from the letter D (colourless) through to Z (light yellow or light brown). Under the GIA scale, D to F grades are classed as colourless, while G to J are classed as near colourless. It is generally difficult for the naked eye to tell D to G colour diamonds apart — the closer a diamond is to colourless, the rarer and more valuable it becomes (fancy colour diamonds are the exception). That said, weight, clarity and cut must all be considered alongside colour when valuing a diamond.

How Diamond Colour Is Graded

Each colour grade has a precisely defined range. Under controlled viewing conditions, a professional grader compares the diamond being graded against a master set of stones representing the D to Z colour range.

How to Choose a Colour Grade

Since D to F grades are all classed as colourless, an F-colour diamond is worth considering for its more accessible price. D colour, of course, remains the highest and most sought-after grade. If your budget is tighter, G or H colour — classed as near colourless — offers a noticeably lower price than the top colour grades.

How Fluorescence Affects Colour Grade

Fluorescence is the visible light a diamond emits when exposed to UV light. About 35% of diamonds fluoresce under UV light, most commonly blue, and sometimes yellow or orange. Blue fluorescence can make a slightly yellow-tinted diamond appear whiter or more colourless. For example, K, L or M colour diamonds with fluorescence can benefit from this effect, appearing a shade whiter. So if you are after a lower price, a diamond of a slightly lower colour grade with fluorescence is worth considering.

Because diamonds form naturally underground, they develop varying degrees of internal characteristics known as inclusions. Clarity refers to how few of these inclusions a diamond has — the higher the clarity, the fewer the inclusions, and a truly flawless diamond is exceptionally rare. Inclusions are commonly thought to affect a diamond's value negatively, but in fact they can also serve as identifying marks, helping to distinguish a natural diamond from a lab-grown one.

How Diamond Clarity Is Graded

A professional grader assesses a diamond's clarity based on four factors:

• Size: The size of the inclusions.
• Relief: How noticeable the inclusions are. Darker inclusions stand out more than lighter ones and have a greater effect on the clarity grade.
• Number: The quantity of inclusions. Very minor inclusions may not need to be factored in at all.
• Position: The location of the inclusions also affects the clarity grade, as it can influence how light is refracted or blocked.

GIA Clarity Grades

• FL (Flawless): No inclusions or blemishes visible under 10x magnification.
• IF (Internally Flawless): No inclusions visible under 10x magnification, only minor surface blemishes.
• VVS1 / VVS2 (Very, Very Slightly Included): Inclusions are difficult to see even under 10x magnification.
• VS1 / VS2 (Very Slightly Included): Minor inclusions are visible under 10x magnification with effort.
• SI1 / SI2 (Slightly Included): Inclusions are visible to a grader under 10x magnification.
• I1 / I2 / I3 (Included): Inclusions are obvious under 10x magnification, and sometimes clearly visible to the naked eye.

How to Choose the Right Clarity Grade

Under normal circumstances, a diamond's size, colour and sparkle are far easier to spot with the naked eye than its clarity. Once a diamond reaches VS1 or above, any further increase in clarity makes little visible difference — meaning VS1, VVS2 and VVS1 diamonds can all look equally beautiful. Naturally, the higher the clarity, the rarer and more valuable the diamond. If your budget is tighter, a lower clarity grade is worth considering for its more attractive price.

What Is an 'Eye Clean' Diamond?

'Eye clean' describes a diamond whose inclusions cannot be seen with the naked eye, without any magnification. Because eyesight and personal standards vary, the definition is somewhat subjective. Generally, if no visible inclusions can be seen with the naked eye alone at a distance of about 6–12 inches from the diamond's surface, it is considered eye clean.

Cut is the key to a diamond's sparkle. Whether a diamond is beautiful depends on how it interacts with and reflects light. This brilliance is governed by three key attributes:

• Brilliance: The total amount of light reflected back out of the diamond.
• Fire: The dispersion of light entering the diamond into flashes of spectral colour — the more colours, the richer the fire.
• Scintillation: The pattern and frequency of light and dark flashes across the diamond's surface as it moves.

A diamond's cut proportions have a direct effect on its sparkle. Two diamonds with similar colour, clarity and weight can look dramatically different because of their cut proportions — one may appear noticeably larger and more brilliant than the other.

Diamond Cut Grades

• Excellent
• Very Good
• Good
• Fair
• Poor

Of the 4C standards, cut has the greatest influence on a diamond's brilliance, fire and scintillation. An excellent cut makes a diamond sparkle brightly, appearing far more radiant than one with a poor cut.

Diamond Structure and Proportions

Viewed from the side, a standard round brilliant cut is made up of three main parts, from top to bottom: the crown, the girdle and the pavilion. A round brilliant has 57 or 58 facets (the 58th being a small flat facet at the base of the pavilion, known as the culet). The large flat facet at the top is called the table. Cut proportions describe the relationship between the table size, crown angle and pavilion depth, which ultimately determines how the diamond interacts with light. A well-cut diamond shows maximum brilliance, while one cut too shallow or too deep allows some light to leak out.

Cut vs. Shape

Cut is often confused with shape, as people assume cut simply refers to a diamond's outer form. Because round diamonds sparkle so brilliantly, most jewellery is set with round stones; other shapes — such as princess, marquise, pear, oval, heart, emerald and cushion — are collectively known as fancy shapes.

What Are 'Hearts and Arrows'?

A perfectly cut diamond, viewed through a special optical instrument, reveals a pattern of eight hearts and eight arrows — an optical effect created by the precise symmetry of its cut. A brilliant-cut diamond has 57 facets; when every facet achieves consistent symmetry, eight arrow shapes appear across the top of the diamond, and eight heart shapes appear when viewed from below.

Diamond fluorescence is the light a diamond emits when exposed to UV light. On a GIA diamond grading report, fluorescence describes the strength of a diamond's reaction to UV light, graded across five levels:

• None
• Faint
• Medium
• Strong
• Very Strong

Under normal conditions it is impossible to tell whether a diamond fluoresces; this can only be seen when the diamond is examined at close range under UV light.

Is Fluorescence Common?

Yes. Of the diamonds submitted to GIA over the past decade, roughly 25%–35% show some degree of fluorescence; of these, only about 10% show any visible effect on appearance, and over 95% of fluorescent diamonds emit a blue glow.

How Does Fluorescence Affect a Diamond's Appearance?

According to GIA research, fluorescence has no noticeable effect on the appearance of most diamonds. In lower colour grades (such as I, J, K, L or M), medium to strong fluorescence can even have a positive effect on colour, making the diamond appear whiter. In rare cases — about 0.2% of GIA's fluorescent diamonds — very strong fluorescence may cause a diamond to look hazy or oily.

Does Fluorescence Affect a Diamond's Value?

Because many buyers misunderstand fluorescence and worry it will affect a diamond's appearance, non-fluorescent diamonds tend to command a slight premium (potentially 10% or more). So if your budget is tighter and the appearance is unaffected, a fairly priced diamond with fluorescence is well worth considering. Fluorescence has no effect on a diamond's structural integrity.

As the global economy faces turbulence, people are increasingly looking elsewhere to invest. Why invest in diamonds?

• Diamonds are easy to carry and require very little storage space.
• Diamonds are exceptionally durable, lasting a lifetime and able to be passed down from generation to generation.
• They hold their value and hedge against inflation, with prices less exposed to political and economic fluctuations.
• You can wear and enjoy diamond jewellery without losing its value — provided the diamond remains in good condition, it can still be resold on the market.
• It is a tangible asset that can be held, worn and owned forever — unlike other 'paper' forms of investment.

Certain diamonds are known as 'investment grade' because they carry greater potential for appreciation and can hedge against inflation. Owing to their scarcity, they offer a degree of appreciation potential beyond that of stocks, bonds and other investment instruments. And, of course, you can wear a beautiful diamond — you cannot wear a share certificate, banknotes, or a gold bar!

What Is an Investment-Grade Diamond?

Investment-grade diamonds are typically white, round brilliant-cut diamonds of a high colour and clarity standard:

• Carat weight: 1 carat and above
• Colour: D to H
• Clarity: IF to VS2