A Buyer's Guide

When jewellery designers are asked what inspires them, they often say that it is the gemstones themselves. That the gemstones ‘speak’ to them. Almost as if they were living objects, individuals with their own personalities and preferences and plans for their future – as if the gemstones were determined to become one particular piece of jewellery and not another.

Emeralds and Rubies


First, buy from a respected jeweller or dealer. If you’re not sure where to start, ask around for suggestions. Word of mouth is usually an excellent way to get helpful, targeted suggestions, especially from like-minded friends or acquaintances.

Alternatively, if you’re in North America, you might try your local Better Business Bureau, or, in the United Kingdom, the British Jewellers’ Association. The website of The International Coloured Gemstone Association, a global organisation, also provides plenty of helpful guidance and contacts. Jewellery specialists at international auction houses such as Christie’s are great sources of expertise and advice.



Once you’ve found a seller you’re comfortable with and a gemstone you like, that really speaks to you, look closely at it. Take your time and don’t be afraid to get hands-on. Pick it up, hold it to the light, turn it around, tilt it this way and that. Ask for a loupe (a special gemmological magnifying glass) to peer inside. Most importantly, try it on and see how it makes you look and feel.

Your jeweller should be able to explain any small marks or blemishes you might see within the gemstone, and tell you how it relates to its own uniqueness and specific composition.

Coloured gemstones are usually ‘treated’ to some extent to improve their appearance. Common treatments include heating (to enhance their colour) and filling (to improve clarity). Treatments are widely accepted within the industry, so it is always worth asking for any details, as treatments can have a bearing not only the value of a gemstone but also how you should set it and take care of it.



If you are buying a gemstone that represents a significant purchase to you as an individual (recognising that this can change from person to person and circumstance to circumstance), ask for a certificate.

Last but not least, and all other things being equal, listen again to the gemstone. If it’s still telling you “I’m the one”, then it probably is the one.

Certification lies at the heart of a buyer’s confidence in, and the credibility behind any gemstone.

Don’t be shy to ask for documentation to understand your gemstone better. A report from a licensed gemological laboratory will confirm the characteristics and qualities of your preferred gemstone, including not only its colour, clarity, weight and dimensions but can also include its country of origin and the presence, if any, of treatments used to enhance the appearance of the gem. Untreated gemstones usually command higher prices. Confirmation of the country of origin can provide some comfort in helping to reduce the risk that the gemstones have supported conflict, child labour or any other unethical practices. Some newer certificates contain the name of the party that presented the gemstone to the laboratory for testing, providing further transparency and comfort. Chain-of-custody certificates may also be provided to identify the original source of the gemstones. Gemfields is working with its industry partners to make available certain laboratory certificates and chain-of-custody certificates containing the Gemfields name.

Character is the very essence of why coloured gemstones are different to diamonds.

The characteristics and value of most diamonds which tend to be more linear in nature, can be well described by four objective measures (being the ‘Four Cs’). This is not the case with coloured gemstones which often are far more multi-dimensional. Like people, no two coloured gemstones are identical. Each has its own uniqueness and character. People have different preferences when it comes to things like art, music and wine. The same is true of coloured gemstones. Ultimately, beauty is in the eye of the beholder. It is entirely acceptable to disagree with the so-called experts based on personal preference. There are no parameters to describe the enchanting, talismanic and emotional engagement of coloured gemstones. As such, coloured gemstones allow us to express our own tastes and individuality and to choose the gemstone that has the most meaning to us – a deeply personal experience. Your gemstone is there to provide you with pleasure, so pick the one you like most.

Colour can have a dramatic impact on price, making it a defining gem characteristic. A gemstone’s colour is described by reference to hue, saturation and tone.

Hue describes the accuracy of the principal colour and the extent to which secondary colours are present. The strength of any secondary colour typically detracts from value. Saturation relates to the vividness, brightness or intensity of the colour. Sometimes this is described as the amount of ‘life’ in the gem.

Tone describes the lightness or darkness of a gem, or the degree to which white or black appears to have been mixed in with the pure hue of the gem. While these colour attributes can seem bewildering, remember that beauty is ultimately in the eye of the beholder, and the appeal of the unique ‘character’ of the gemstone to the specific buyer is key.

Despite all of the above many experts in the field would advise consumers to “buy what they love”. This is perhaps one of the most unique factors relative to coloured gemstones as they are just as diverse and interesting as we are as humans, meaning that every person has the opportunity to find something that is special and meaningful to them

Clarity typically ranks after colour when evaluating coloured gemstones. It describes the extent to which a gemstone contains inclusions and fractures.

The fewer the inclusions, the better, as this enhances transparency and brilliance. That said, emeralds are famous for having visible inclusions known as ‘jardins’. These feather-like inclusions are a natural part of the gemstone and give the gem its unique character.

Eye Clean Slightly included Included
Very Significant
Illustrations courtesy of CIBJO.

Cut describes the shape into which the rough gemstone has been cut and polished in a lapidary.

Cut is typically divided into faceted gems (gems with geometrically shaped flat faces) and non-faceted gems (gems with rounded surfaces, generally called cabochons). Value is enhanced when a gemstone is well proportioned and symmetrical, has been well polished and possesses good lustre.

Drag the gemstones to explore different types of cut

Emerald Cut
Tapered Baguette
Antique Cushion
Heart Shape
Princess Cut
Illustrations courtesy of CIBJO.

Gemstones are typically sold by the carat,
a unit of weight not size.

The word ‘carat’ comes from the ‘carob’ seed, the original unit of measurement for gem traders. Today, a carat is equal to exactly 0.2 grams, meaning there are 5 carats in a gram. Each carat can also be divided into 100 ‘points’.


In 1812 the Mohs scale of mineral hardness was devised by the German mineralogist Frederich Mohs (1773–1839), who selected the ten minerals because they were common or readily available.



Mineral: Talc 1

Associations: Talcum powder.

Mineral: Gypsum 2

Associations: Plaster of paris. Gypsum is formed when seawater evaporates from the Earth’s surface.

Mineral: Calcite 3

Associations: Limestone and most shells contain Calcite.

Mineral: Fluorite 4

Mineral: Apatite 5

Mineral: Orthoclase 6

Associations: Orthoclase is a feldspar. Moonstone is a variety of Orthoclase.

Mineral: Quartz 7

Associations: Amethyst is a variety of Quartz and is the February birthstone.

Mineral: Topaz/ Beryl 8

Associations: Emerald is the May birthstone. Emerald and aquamarine are varieties of Beryl with a hardness of 7.5.

Mineral: Corundum 9

Associations: Sapphire and ruby are varieties of Corundum. Twice as hard as topaz. Ruby is the July birthstone. Sapphire is the September birthstone.

Mineral: Diamond 10

Associations: Used in jewellery and cutting tools. Four times as hard as Corundum.