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Choosing a gemstone

Ametrine and Diamond ringWhen choosing a gemstone, whether this is for an engagement ring, when you’re designing a special and unique piece, or even to replace a lost stone, it can be a daunting task.

How to buy a gemstone isn’t something you can simply Google and expect to become an instant expert, but there are some things you can be aware of before you make your decision.  Of course, the first thing you need to be aware of is how trustworthy your chosen supplier is.  You will need to rely on your jeweller to make sure you find the best gemstone for your budget and your desire.

There are several key factors that add together to set the value of every stone you consider. 

The most obvious one is size, or weight, which is measured in carats.  However, bigger doesn’t necessarily mean better.  A stone is also valued by its clarity, colour and cut.

White emerald cut diamond engagement ringClarity

In some gemstones clarity is less vital than in others, but unless a stone is totally opaque, such as an opal, how light passes through the stone affects its beauty and therefore its worth. 

Within gemstones you will find a quantity of spots or lines, called inclusions. In short, for most gems, the fewer the inclusions, the more valuable the gemstone, as these can interfere with the movement of light through the stone, reducing the sparkle and value of the stone. Clarity is absolutely key with diamond valuation, for example. A two carat diamond with a high inclusion count can be less valuable than a one carat stone with high clarity.

Some gems have naturally very few inclusions to interrupt the light flow, such as Tanzanite, meaning that other factors take precedence when valuing this stone.  Others have characteristic inclusions, some emeralds for example have a “jardine” (garden) of inclusions, which makes each gem truly unique.

Natural ruby in 18c white gold with diamonds flankingColour

When we say ‘colour’ we don’t just mean blue sapphire, red ruby or green emerald, for example.  Every gemstone has a range of colours, with some more rare and so more valued than others.  You will be aware of canary (yellow) diamonds and pink sapphires, for example.  Even so called ‘white’ diamonds vary in how white they actually are and are measured against an internationally recognised scale, from D (colourless) to Z (light coloured).  The value is greater the closer to D your stone is.

Coloured gemstones – sapphires, emeralds, citrine, topaz, etc – are also measured on a scale, which is designed around three key points: Hue, the dominant colour; Tone, how light or dark the colour; and Saturation, the intensity of the hue. 

This can of course get complicated, so we say buy what you love. Ask to see several examples of the colour of stone you want and don’t restrict yourself to one gemstone type – you can find pink diamonds and sapphires, red rubies or tourmaline, green emerald or peridot, etc, and each will bring different characteristics with it.

Trillion cut pink tourmaline pendant, with white diamondsCut

The way a gemstone is cut will enhance its sparkle and shine.  The most talented gem cutters get the very best from the gemstones they work on, with a dazzling end result.

 Consumers must reconcile their budget with their tastes. A smaller gem of finer quality will cost as much or more than a larger gem of lesser quality. Nature produces far fewer of the top quality gems, so there is good reason for the greater price. The following is a summary of factors for some of the most popular gems in the trade.

Green tourmaline and diamond dress ringTreatment

Coloured gemstones with the type of colour we love the most don’t occur as frequently as you might think.  In many, the colour you see has been achieved due to some form of treatment.  Many rubies are heat treated for example to achieve the hue we require.  Gems may be treated with heat or with safe irradiation to achieve the colour we desire.  ‘Natural’ gems – gemstones in which sought-after colour is naturally occurring – are generally more valuable because of their relative rarity.


Yes, some precious stones are more hard wearing than others, meaning you need to consider how you want to have your stone set and how you will wear it before you make a final decision on which type of stone you want to buy.

Diamonds, sapphire, ruby and garnet are highly durable and so are well-suited to an active daily life and work well in rings, bracelets or cufflinks.  Others, such as emeralds, pearls and opals are slightly more fragile and so need mounting and wearing accordingly. 

Here at Christopher Evans we’re expert in sourcing and selecting fabulous gemstones of all colours and kinds.  In fact, we have a passion for coloured gemstones and can present you with a dazzling array of more unusual and interesting gems, as well as diamonds in all sizes and colours.

Call in or call to make an appointment; your journey to the perfect gemstone for you starts here.