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A guide to diamond cuts, shapes, clarity, and colours

Guide To Diamonds

Diamonds are prized all over the world for their dazzling sparkle and ‘fire’. Seen as the epitome of luxury gifting, they can mark some of the most important and emotional moments in life.

If you’re looking to invest in a diamond soon, it will help to know more about how this famous gemstone is assessed and valued by gemmologists, so you can find the best stone for your money. Below is a handy guide on diamond cuts, shapes, clarity and colour, so you’ll know exactly what to look for when shopping for that perfect sparkler.

What are the 4 Cs of diamond quality?
When assessing any diamond, a gemmologist (that’s someone who is an expert at valuing gemstones) will always use the 4 Cs: cut, colour, clarity, and carat weight of a diamond.  Below is a description of each and what you need to look out for when shopping.

Diamond cuts

Contrary to what many people believe, the cut of a diamond does not refer to its shape: it actually means the way the diamond has been proportioned and polished. The cut is what determines how well a diamond ‘sparkles’ and the way it catches and reflects light.

A diamond is nothing if it's not cut properly. The more expertly a diamond is cut, the more dazzling the sparkle will be (this effect is also called ‘dispersion’). Days, weeks, or even months of painstaking work is often put into cutting a single diamond to show off its best features.

There are lots of different diamond cuts, each with different patterns and facets which reflect the light in their own unique way. As a rule of thumb, the more intricate the cut, and the more skilled the cutter, then the more luminous the finished diamond will be.

One of the most popular cuts is the modern ‘round brilliant’, which has been mathematically proportioned to reflect maximum light and provide plenty of sparkle and fire. As a result, this is a very common style for diamond engagement rings. All other types of diamond cut are known as ‘fancy cuts’.  

When looking for a well-cut diamond, you’re essentially just looking for a diamond that reflects plenty of white light, and a brilliant level of fire or dispersion coming out of the stone. The stone should look lively throughout and have no darkened or cloudy areas. If it looks luminous and catches the light brilliantly, then it’s a sign of a quality cut.

Diamond shapes

The shape of a diamond refers to the design of the gemstone. Unlike the cut, this isn’t an indicator of the quality of a diamond, and the shape won’t change the lustre and sparkle. So, when choosing a diamond shape, it’s all really a matter of your own personal preference.

Below, you can see several examples of some of the most popular diamond shapes:

Diamond Cuts Guide

Different shapes go in and out of fashion, the classic round brilliant shape and cut is most popular. But many fancy cuts have also been popular over the years:  the art deco style with a baguette or emerald cut was all the rage in the 1920s, while oval styles soared in popularity during the 80s after Princess Diana received an oval engagement ring. In recent years, heart-shaped diamonds have grown in popularity, especially when given as a romantic gift.

Certain shapes are also better suited to different items of jewellery. For instance, a marquise or oval diamond ring will extend the line of the hand, making the fingers to look longer and slimmer, while the droplet shape of a pear diamond makes it an elegant choice for a pair of earrings.

Diamond colour

The colour of white diamonds is not measured in terms of how vividly it is coloured — it’s actually the other way around, with the ‘colour’ being graded according to the absence of colour from a diamond. In other words: the whiter the stone, the higher it will rate on the grading scale.

Colour is graded against the Gemmological Institute of America (GIA) grading chart, which runs from D–Z, with D being the clearest and whitest. Gems which score highly on the scale tend to be more expensive, and even the slightest tinge of colour can have a dramatic effect on a diamond’s value.

A colourless diamond is usually considered the ‘best’ quality in traditional terms of rarity and value, but, ultimately, the gem you choose is down to personal preference. Some people like the warmth of a diamond with a hint of yellow.

While most diamonds fall into this chart, nature does occasionally throw a curve ball our way, as diamonds can be found in a variety of colours, from pink and red to blue and green. These gems are often prized for their unique beauty and will sometimes cost more than a clear diamond.

 Diamonds Guide Image

Diamond clarity

The clarity of a diamond is graded on how absent or free of inclusions or blemishes a diamond is. This is graded in a similar way as colour, using a standardised scale.

Inclusions are the amount of imperfections and their locations inside of the diamond — the fewer there are, the more valuable the stone becomes. Blemishes are the amount of imperfections on the outside of the stone. Again, the fewer of these, the better.

Gemmologists and graders use the diamond clarity scale to describe and measure inclusions and blemishes. Much like the colour scale, this was introduced and decided by the GIA.

The diamond clarity chart consists of six different grades, all with sub grades inside of them. Below are the grades and their criteria:

Flawless (FL)

The absolute pinnacle of quality in diamonds, this means no inclusions and no blemishes at all inside or outside the stone. Absolute perfection. These are the stones we would all love to own. However, much like very large or colourless diamonds, these very rare stones usually come with the price tag to match.

Internally Flawless (IF)

Completely free of any inclusions (on the inside of the stone) but may have a slight or tiny imperfection (or blemish) to the outside of the stone.

Very Very Slightly Included (VVS1-VVS2)

This clarity grade is split into two sub grades to differentiate between levels of quality, with 1 being the higher grade. VVS stones have either inclusions or blemishes and sometimes both, but these imperfections are minute and are extremely or very difficult to find. These would even be hard for a skilled grader to see under 10x magnification, and they are still a very high-quality.

Very Slightly Included (VS1-VS2)
The imperfections in these stone are minor and for a skilled grader can be found under 10x magnification. Again, very slightly included is split into two sub grades, with 1 denoting a higher value than 2. These stones still carry a lot of value, especially when combined with a quality cut and excellent colour.

Slightly Included (SI1-SI2)

Slightly included stones show inclusions or blemishes that can be found easily by a skilled grader when put under 10x magnification. There are two sub grades, with one denoting a higher value than two. These are more common than the higher grades, but still denote a value, especially when coupled with a desired colour.

Included (I1-I2) or (P1-P2)

Included stones have obviously visible inclusions that can be seen without 10x magnification, and maybe seen by the untrained eye as well as a skilled grader. They may also have inclusions that threaten the structure of a stone. These stones still denote a value (they are still diamonds, after all) but not as high as the clarity gradings explained above.

Carat Weight

A carat is a unit of measurement used to denote the weight of a diamond. The word ‘carat’ takes its name from the carob seed, which was used as a unit of measurement by ancient Mediterranean and Middle Eastern gem dealers. Merchants would use these to calibrate their scales when weighing out gems, with 1 carob being equivalent to 1 Carat. When using the metric system, 1 carat of diamond is the equivalent of 0.2 grams.

While carats don’t measure the size of a diamond, as a general rule, a heavier diamond will also be bigger. As with all the other Cs, the bigger the stone, the higher the value. The Cullinan diamond — the largest ever found — weighed in at a whopping 3,106.75 carats, which is equivalent to 621.35 grams!

Diamond Weight Guide

At Est. 1897, we have a huge assortment of stunning pre-owned jewellery, including diamond necklaces and rings, all of which have been assessed, professionally cleaned, and refurbished to a high standard, so you can count on them to be excellent quality.

So, if you’re looking to invest or buy some diamond jewellery as a gift, you can get dazzling, top-quality gems for a fraction of the price of a brand-new piece.

If you have any questions about our jewellery or want help to find a diamond with a particular cut, shape, clarity or colour grade, get in touch with the Est. 1897 team.