Every diamond is completely unique and as such will have it own characteristics, these characteristics are broken down into 5 simple industry accepted categories or grades all of which determine the stones value. As each stone is completely unique, the price for a certified stone is also completely unique. It is down to the job of the skilled stone cutter to create the best stone possible from the rock.

Choosing diamond jewellery can be overwhelming, but to simplify the search Béo guide to buying diamonds explains the five grading types and advises on the range available.

As individual as the precious stone is the customers tastes, like any object of beauty it is in the eye of the beholder. The most imperative factor in choosing your diamond is choosing a stone that looks great to your eye and appeals to your values, and your budget. When viewing many stones you will soon realise that a few will jump out at you straight away.

The essential information to help you to make an educated purchase is listed below:


A diamond certificate is a report completed by a qualified gemmologist informing you of one specific stones many characteristics. The most widely discussed of these qualities are named the 4Cs; Cut, Colour, Clarity, and Carat weight.  Shape, symmetry, florescence and polish are also analysed although discussed less. 

For diamonds larger than 0.30ct a wide range of stones are available with certificates, however they do incur an extra cost. Independent laboratories use world wide industry accepted tests to compile the information given on the certificate which includes its’ own tracking number and certification. This protects the value of your diamond should you need or wish to resell it.

The GIA ( Gemmological Institute of America) is among the most respected laboratory in the industry. Having a GIA certificate adds value to your stone.  Certified stones are available at Béo, however as each stone is unique and is updated daily contact info@Béo.london for a quote.  Prices given on the website are for uncertified stones


THE 4CS + 1S

The value of a diamond is determined by Shape, Carat, Cut, Clarity and Colour.



By far the most popular shape in Diamond is the round brilliant.  For those who like to have something outside of the norm there is an array of non-round shaped stones, which in the jewellery industry are called fancy shapes. Certain shapes such as; emerald, baguette, asscher and square or step cut all have a larger table which highlights the clarity of the stone.  It is therefore advisable to stick with a higher clarity on these stones.  We recommend VS2 or above.

Stone Shape


Why you'll love it:  Precise mathematical calculations have been used to design the round brilliant proportions and number of facets. This cut naturally follows the rough diamond crystal, which is why it is also referred to as the ideal cut. The brilliant cut allows the light to enter through the top of the stone, refract (bounce off the facets on the sides) and back out again through the top of the stone. The most popular and certainly one of the most sparkly cuts is the round brilliant cut which has 58 facets including table and culet


Why you'll love it:  Second most popular stone shape. Traditionally square in shape, however can also be found in rectangular shapes see length to width ratios below, a more square cut stone look for ratios between 1 -1.05

Princess Ratio


Why you'll love it:  Square step cuts whose corners are not truncated are known as carré; they are also characteristic of antique jewelry. They may resemble the square-shaped Princess cut in passing, but a carré's simpler facets are distinctive.  They may or may not have a culet. In Western jewelry dating to before the advent of brilliant-type cuts, very shallow step-cut stones were used as lustrous covers for miniature paintings: these are known in the antique trade as portrait stones. Characteristic of Indian jewelry are lasque diamonds, which may be the earliest form of step cut. They are flat stones with large tables and asymmetric outlines


Why you'll love it:  The Oval beautiful brilliance and elongated shape can accentuate elegant long fingers.  The proportions of the oval cut vary with the most traditional cut length to width ration being between 1.33 and 1.66.  See below for a visual guide.

Oval Ratio 


Why you'll love it:  The Marquise beautiful brilliance and elongated shapes gives the illusion of a larger stone, a great compliment to a longer finger and something different to the norm.  The proportions of the marquise cut vary with the most traditional cut length to width ration being between 1.75 and 2.25.  See below for a visual guide.

Marquise Ratio


Why you'll love it:  A unique cut with rectangular facets, the original shape was designed for the emerald stone type, as it reduced the amount of pressure exerted on the stone. The term “emerald cut” can be traced to the Art Deco period, the stone was widely used in this period and as such is as a nod to vintage jewellery seen in this era.  The proportions of the emerald cut vary with the most traditional cut length to width ration being 1.4, those looking for a more square ratio will opt for a lower ratio and higher for those who like a more rectangular stone. See below for a visual guide.

Emerald Ratio


Why you'll love it: An exceptional cut nearly identical to the emerald, with the omission that it is square. Named after the inventor of the cut Joseph Asscher, who later cut the famous 3’106ct Cullinan diamond for the English Queens crown.  As discussed earlier, we advise clarity of VS2 and above, or check out the plot map of a lower grade stone because this stone will highlight the clarity.  As the asscher is square the proportions of the asscher cut are length to width ratio of 1.0-1.05.  See below for a visual guide.

Asscher Ratio


Why you'll love it:  This brilliant cut is known to create a slimming effect on your finger, is also the perfect shape to use in a drop necklace and earrings.  A unique blend of the round brilliant and marquise cut. It is advised to go for colour H and above in this cut as colour can be more visible at the tip.  The typical proportions of the pear cut are length to width ratio of 1.5-1.75  See below for a visual guide.

Pear Ratio


Why you'll love it:  This organic vintage cut stone is beautifully cut With 58 facets, designed to look great under incandescent light. It is the predecessor of today’s modern round brilliant cut. Like the old mine cut, diamonds cut into this shape possess a high crown, small table. However, the old European cut has a circular girdle. The Old European cut dates to the 1800s and was used mostly during the Victorian, Edwardian, and Art Nouveau eras.


Why you'll love it:  The rose cut features a flat bottom with a dome-shaped crown, rising to a single apex. With anywhere from 3 to 24 facets, a rose cut diamond resembles the shape of a rose bud. The rose cut dates to the 1500s and remained common during the Georgian and Victorian eras.


Why you'll love it:  Elegant, slender, rectangular baguette cut (from the French, resembling a loaf of bread) is the most common form of the step cut.  It most often used as an accent stone to flank a ring's larger central stone or channel set into a band ring. Synonymous with the art deco period and available in a tapering  rectangular cut know as tapered baguette cut.


Carat weight measures a diamonds weight and is the most obvious factor in valuing a diamond as it refers to the stones overall size. One carat (1ct) weighs 1/5 of a gram (about the same as a five pound note) and it is divided into 100 points. So a 50 pointer is a diamond of 0.5ct or half a carat in weight. Depending on the cut proportion and shape of the stone, the diameter of the table ( top of the stone) can vary, a 1ct brilliant cut measures approximately 6.5mm in diameter and a 0.5ct stone about 5.2mm.  A rose cut is a lot more unpredictable in mm size to carat weight as it is more organic in form.  See the size guide below for me mm size to carat weight

Carat weight does not affect the value of diamonds proportionally though. The larger the stone the more disproportionate is the increase in cost per carat. As with many industries greater demand increases the cost, the most sought after carat weights; 1.00ct, 0.75ct, 0.50ct, 0.33ct, 0.25ct are also the most expensive.  You may get better value for money for a stone just under the popular ct weights; 0.98t, 0.74ct, 0.49ct, 0.32ct, 0.24ct, the price increases significantly once a stone hits the 1ct mark.



Cut of a diamond is one of the important attributes as it determines the brilliance, fire and sparkle of the stone. Cut and Shape should not be confused, although easily done.  Poorly cut diamonds do not reflect as much light through their main surface (“table”) therefore may be dull. Diamonds are either shaped by hand by skilled diamond polishers or by complex machines.  Prior to 2005 GIA (Gemmological  Institute of America) employs a five point scale ranging from: Excellent - Ideal cut - Very good – Good cut– Fair cut – Poor cut



A gemmologist assesses the clarity of a gemstone for inclusions and blemishes. The former being described as diamond crystals or foreign materials surrounded by the stone.  With the later described as external objects affecting the stones surface.  The stones are analysed under a loupe, which magnifies x10. The fewer of both of these the higher the clarity grade, more exceptional and expensive a stone will be.  Size, type, nature and appearance of the inclusions also effect the grading.

Almost all diamonds contain minute traces of non-crystallized carbon or small non-diamond crystals.  A certified stone will have a map showing in type and position of the inclusions.  The Skill in selecting a stone in a lower clarity is to ensure the inclusions are hidden, are not cracks and are colourless or embrace them as unique quality or fingerprint of your stone

A flawless stone is incredibly hard to come by, especially in bigger stones, but most inclusions aren’t visible to the naked eye anyway. Also, some inclusions such as Garnet or Ruby crystals can make your diamond very unique and special. Please see the chart below for more about inclusions.




Colour or lack of colour in a diamond is another important factor. The ideal colour is actually colourless, however fancy diamonds with an intense hue such as blue, red, pink, yellow, black or green can be held in even higher esteem. GIA colour grading starts from D at completely colourless and goes all the way up to Z+.  With Z+ being fancy coloured stones.

Gia chart is shown below.

Diamond Colour

For Diamond Care see here