Diamond Properties and Characteristics

Last updated on April 9, 2021

Being the official birthstone for April, diamond is the most famous and popular of all gemstones. It is one of the four recognized precious gems along with emerald, ruby and sapphire and the hardest substance on earth. No gemstone contains as much charm and interest as does diamond.

Diamond Origin and Formation

Diamond is a transparent, gem-quality crystalline form of carbon, and it is the hardest substance on earth. The name diamond comes from the Greek “adamas”, meaning “invincible” or “invulnerable”, which is a sheer testament to its superior hardness.

Most natural diamonds were formed under extremely high temperature and pressure that naturally exist deep inside the earth, typically at depth of over 140 kilometres where temperatures are at least 1050° Celsius. Under these conditions, each carbon atom forms a covalent tetrahedral bond with four adjacent carbon atoms for billions of years and gives us diamond. This formation yields a strong three-dimensional cubic structure, allowing refracting light in all directions at the same velocity.

After the diamonds were formed, some were brought to the surface through deep volcanic eruptions of magma millions of years ago. Many diamonds remain intact embedded in the solidified ingenious rocks called kimberlite, which also contain many other minerals like calcite, diopside, garnet, olivine, serpentine and small amounts of apatite.

Diamonds are found in over 30 countries all over the world. The production levels of diamonds vary year by year, but as of 2020, the top diamond producers were Russia (23,000,000 carats), Botswana (16,000,000 carats), Canada (13,000,000 carats), Angola (8,500,000 carats), South Africa (7,700,000 carats), the Democratic Republic of Congo (3,700,000 carats), Namibia (1,900,000 carats), Lesotho (1,100,000 carats), Australia (340,000 carats) and Tanzania (260,000 carats).

Diamond Colour

Diamonds are typically known to be colourless, but most diamonds mined come with noticeable yellowish and brownish tints, and only a small percentage of them can be classified as colourless or near-colourless. Moreover, even the stones with faint yellowish hues are rare to find.

According to the Gemological Institute of America (GIA), the colour of colourless diamonds is graded on a scale from D to Z, with D being the most colourless, and Z containing brown or yellow tint noticeable to the naked eye. Colour is graded under controlled conditions by comparing a diamond to round brilliant diamonds of known colour, called master stones.

The D-to-Z colour scale is the industry standard for grading colourless diamonds where each letter represents a range of colour based on a diamond’s tone and saturation:

• D-E-F – colourless
• G-H-I-J – near colourless
• K-L-M – faint yellow
• N-O-P-Q-R – very light
• S-T-U-V-W-X-Y-Z – light

The world of diamonds is not limited to colourless stones. There are rare specimens that come in a variety of colours. Such diamonds are commonly called “Fancy Colour Diamonds” or simply “Fancy Diamonds”, and they come in almost any colour one can imagine.

The colour evaluation of fancy diamonds is based on the strength of their colour and has three main components: hue, saturation and tone.

Fancy diamonds owe their colour to the presence of various trace elements in their structure or crystal lattice defects. For example, golden or brownish hues are owed to nitrogen impurities, blue diamonds are coloured by boron impurities, while green diamonds are coloured by a small content of radioactive chemical elements such as uranium or thorium.

Diamond Clarity

The majority of diamonds found in nature contain lots of inclusions, and it is hard to find a stone with only a couple of visible flaws. In fact, only roughly 20% of all diamonds mined are of any gemstone value.

Clarity is one of the main characteristics of a diamond that grades how clean the diamond is from any kind of inclusions (internal flaws) and blemishes (external flaws). It has a significant impact on a diamond’s value, meaning the fewer inclusions and blemishes the diamond has, the better its grade and the higher its value.

According to the Gemological Institute of America (GIA), diamond clarity is graded on the following scale:

• FL (Flawless) – no inclusions and blemishes visible under 10x magnification.
• IF (Internally Flawless) – no inclusions visible under 10x magnification.
• VVS1, VVS2 (Very Very Slightly Included) – hardly noticeable and very small inclusions visible under a gemological microscope.
• VS1, VS2 (Very Slightly Included) – minor inclusions visible with effort under 10x magnification.
• SI1 and SI2 (Slightly Included) – easily noticeable inclusions under 10x magnification.
• I1, I2 and I3 (Included) – obvious inclusions visible with the naked eye.

Although this clarity grading scale is considered official, an assigned clarity grade for any single diamond can vary depending on the laboratory. It is not uncommon for a single stone to be given different clarity grades by different laboratories – the same is true for the colour and cut quality grades.

The clarity of fancy colour diamonds is graded on the same scale – the fewer inclusions, the higher the clarity grade. High clarity fancy diamonds are more valuable, but this characteristic is tolerated more than in colourless diamonds.

Diamond Cut

The cut refers to the precision of angles, proportions, symmetry and polish, which in turn directly impact a stone’s fire, brilliance and scintillation.

In terms of cut quality, the diamond cut should not be confused with both the diamond shape, which can be round, oval, cushion, pear, etc., and the facet arrangement, which can be brilliant or step.

The Gemological Institute of America (GIA) grades round brilliant diamonds on a five-point scale of Excellent, Very Good, Good, Fair and Poor, where Excellent cut grade diamonds provide the maximum brilliance and sparkle. As for the other cuts, GIA does not provide cut grading, but some parameters help evaluate the stone’s cut quality.

The diamond cut grade is based on seven factors – brightness, fire and scintillation (how the diamond appears when viewed face-up), weight ratio and durability (how well it is designed to ensure durability and optimal weight), polish and symmetry (quality of craftsmanship). The grade is set by the lowest assessment the diamond receives for five out of the seven factors. For example, if a diamond is graded Poor for brightness, then the highest overall cut grade can be Poor. However, there are exceptions for polish and symmetry. A diamond with Very Good polish and symmetry may receive an Excellent overall cut grade.

The cut quality is the biggest indicator of a diamond’s beauty and should be made a priority over other characteristics. A colourless or flawless diamond will look dull and lifeless if it is not cut exceptionally well. Poor precision, proportions and symmetry give no brilliance and sparkle.

Unlike colourless diamonds, fancy colour diamonds are not cut to maximize brilliance and sparkle. These diamonds are cut to achieve the best colour possible. In other words, the proportions that are considered ideal for colourless diamonds will not always be the best to bring out the colour of fancy diamonds. So when choosing a fancy diamond, you should focus more on the stone’s colour intensity and hues, rather than judge the diamond using traditional cut grades.

Diamond Carat Weight

The physical weight of diamonds is measured in carats (ct). This measurement originates from the ancient method of weighting precious metals and gemstones against a seed of the carob tree. At the time, carob seeds were considered to be even in weight and were used as weighting references by traders. As you could guess, carob seeds varied in sizes, and the actual weight of the gems could vary by around one metric carat.

It wasn’t until 1907, at the Fourth General Conference on Weights and Measures when it was agreed upon that one diamond carat would be equal to 200 milligrams or 0.2 grams. Nowadays, carat weight is measured using a highly accurate and calibrated digital scale capable of measuring even extremely small weights.

In terms of gemstone weight, there is also the term “point”. A point is one-hundredth of a carat, and 100 points are equal to 1 carat.

Carat is not how large a diamond is. Two diamonds of the same carat weight may differ in size depending on their cut quality and shape.

Carat weight is one of the four main components (4 Cs) of a diamond, along with colour, clarity and cut, that indicate the quality of the stone and determine its value. Diamond price increases with carat weight because larger diamonds are rarer and more desirable as a result. However, two diamonds of the same carat weight can vary in prices depending on the other three factors of the diamond and other pricing criteria.

Diamond Care and Cleaning

Diamond is the hardest and most durable gemstone, 10 on the Mohs hardness scale. While it is an excellent jewellery gemstone for daily wear, it still requires some little maintenance.

Diamonds are typically insensitive to household chemicals, but the precious metals used for the mountings and prongs can get damaged, so make sure you do not wear your diamond jewellery when in contact with bleach and sulfuric acid.

Remember to put your diamond jewellery on last when dressing. Residue from makeup, hairspray, perfume and body creams can damage the setting or make the centre stone look dull. Putting your jewellery on should always be the last step.

To clean diamonds at home, you should add some mild dishwashing soap liquid to warm water. Stir the water and dish soap together using a spoon or your finger. Carefully place your gemstone in the liquid you have prepared and soak it for about 20-30 minutes. This will help to loosen any dirt.

After soaking, use a soft toothbrush to remove the dirt. Brush your jewellery gently not to loosen the prongs, paying particular attention to all sides and edges. Make sure you clean the lower part of the gem as well. The base of the mounting underneath the stone is where a lot of dirt builds up. Next, rinse out your piece of jewellery with clean water and dry it with a soft and lint-free cloth.

When storing diamond jewellery, keep it separated from other softer gemstones to protect them from being scratched. Similarly, you will want to protect your diamonds from other diamonds you have, meaning it is a good idea to store your gems in individual cloth jewellery bags.

Diamond Properties