Sustainable luxury, centuries of craftsmanship

Buying Precious Stones

Guide to buying:

Precious Stones

Guide to buying:

Precious Stones

Precious Stones
Precious Stones

We often get asked questions like ‘how much should a ruby cost?’.

This is of course a very important question to consider. If you wanted a simple answer however, then you’ve come to the wrong place. For coloured stones like ruby, sapphire and emerald there have been many fruitless attempts by the industry to create grading systems - so while we’d love to present a little table below, neatly labelling how much you can expect to pay per carat, it’s just not that simple.

We'll do our best to give you a rough idea of what determines value in the three most valuable coloured stones: rubies, sapphires and emeralds. We’ll go through the common factors used to determine their value, and we hope it will give guidance to you when buying.

Before we start though, remember that you always need to look at the stone itself - you should love what you’re buying, and a big part of that is how it looks and how it makes you feel. That look in turn is determined in a big way by the interplay the stone’s colour and clarity.

Also, there’s carat weight - like for like, the heavier (and larger) a stone is, the more valuable it will be - that probably should be obvious so we’re not going to go into depth on that one! Then there’s the cut, which is whole other topic that’s too intricate to get into here, but is a key part of the stone’s appearance and should also always be taken into account.

Then, behind the scenes, there’s also the stone’s origin and treatment to cover. Finally, we’ll go through what each of these mean for ruby, sapphire and emerald.

The Factors

There’s a lot to cover, so we’re going to take a moment to give you a brief introduction to some the factors to consider.



When using the word ‘colour’ indiscriminately it becomes easy to oversimplify. So we’re going to subdivide ‘colour’ into three components:

Hue - The 'base' of the overall colour i.e. blue or yellow.

Tone - The shade of the colour i.e. light or dark.

Saturation - The strength of the colour i.e. deep or dull.


There a myriad of beautiful, subtle colours out there, and all are worth your consideration. If we’re talking about the value of sapphires, rubies and emeralds, however, then there’s definitely a winning formula: a pure, unadulterated hue (as in ‘blue’ - not ‘greenish blue’), mid-tone (neither too light nor too dark), and strong saturation (as strong as you can get) will be the most valuable colour. In short, the most expensive colours are pure, bright and strong.



Clarity is also important but not a factor that should discourage you from buying a coloured gemstone. Clarity refers to how easily you can see through the stone, and how many inclusions the stone has. Stones such sapphire, ruby and emerald very commonly have inclusions, and while a few small ones are to be expected and definitely form part of a stone’s individual charm a totally flawed stone should be avoided, luckily we have none of those! We’re more tolerant of inclusions in some stones than others (emeralds in particular) but the general rule is this: the fewer inclusions, and the less obvious they are, the more valuable the stone will be. The clarity of a ruby or sapphire should be considered but not something we need to touch on, however, a sapphire or a ruby displaying a spread of inclusions should be avoided where possible. Emeralds we can forgive; as a flawless (or even near flawless) emerald is incredibly scarce.



Origin is where a stone comes from in the world. For some stones, like diamonds, for example, where they were mined has a very limited effect on their value and saleability in most cases. With precious coloured stones, however, history looms large, and their origin is an extremely important factor in the overall value, sometimes to the extent that it outweighs other criteria. Each of the three stones we'll discuss has a traditional hierarchy of origins.



Treatments are used to improve a stone’s appearance or durability through an artificial process. We can tolerate particular treatments in some stones, but the general rule is, the less treatment the better. The two main types of treatment we’re going to be referring to in rubies, sapphires and emeralds are heat treatment and oiling.

In case you’re wondering, heat treatment and clarity enhancement are long-established and fully accepted treatments in the jewellery trade, as long as they are disclosed when the stone is sold (We also stick to this). The easiest way to ease any concerns is to have a certificate from a reputable gemological laboratory, which we provide with the majority of our stones.

The Stones

Now we’ve discussed those common factors, let’s talk about what they mean for each stone. Just to clarify, we’re only talking about natural stones here - not synthetics.


Rubies are a variety of corundum, which is a crystal of aluminium oxide and tinted red. The red is caused by the element chromium. Of all coloured stones, they are the most valuable per carat.



The closer a ruby can get to a pure red, the better, but they’ll often have secondary hues as well, including pink, purple, brown and orange. There are extremely attractive examples of each, but the most valuable rubies have a shade of pure, highly saturated red known as ‘pigeon’s blood’. Many people in the trade will have their own description of this colour and their own opinion on which stones meet the required criteria. In practice, however, the real judges of whether a ruby is ‘pigeon’s blood red’ are the laboratories. When ‘pigeon’s blood’ appears on a certificate, the price of the stone can jump significantly, and this is where world record prices per carat are achieved.



Myanmar: By far the most highly valued rubies are from their most historically renowned source - Myanmar (which is still often called ‘Burma’ in the trade). Burmese rubies in general tend towards a saturated, slightly pinkish red, and typically fluoresce a bright pink under UV light, which is also visible in bright sunlight, giving the stone a distinctive glow.

This is a great example of a high quality Burmese ruby. It’s a strong, saturated red, with good clarity, free from treatment.


Thailand: Another historic source of superb rubies. Generally speaking, they aren’t as pink compared to Burmese stones, and tend towards a slight brown or purple as secondary hues. They also tend not to fluoresce as much as Burmese rubies, which is usually attributed to a stronger iron content. In terms of value, they’re a very respectable second down the list.

Mozambique, Tanzania and Madagascar: In recent years, several deposits of rubies have been found in Mozambique and Tanzania, as well as in Madagascar. These deposits have yielded magnificent rubies in bright, saturated reds, which in some cases have rivalled the fabled ‘pigeon’s blood’ red of the finest Burmese and Thai stones. More generally however, these Southeast African stones tend to display a stronger, scarlet hue, with more of a fiery orange secondary hue, leading them to be described as ‘fire engine red’. As they are newer and less established deposits with a less established market, these rubies are currently lower down the pricing scale than their Southeast Asian counterparts. However, with important jewellery houses such as Cartier and Bulgari taking notice of their excellent quality and vibrant colour, this may well change in the long run.



Rubies are commonly included stones. Heating them can help with that; healing fissures, melting crystals and overall making the stone look more transparent. Heat treatment in rubies is very common, but it should always be disclosed. Heat treatment does reduce a ruby’s value significantly - in real terms it can be by over half, so it’s definitely something you need to know about.


Sapphires are every other variety of corundum apart that isn't a ruby. Most famously sapphires are blue, but they are also found in yellows, pinks, purples, greens and colourless varieties, as well as a peachy orangey pink hue known as ‘padparadscha’.



Sapphires have a huge variety of colours, and while the rule of thumb still applies, where the more pure, saturated colours will command higher prices, paler sapphires are also much-loved. While there’s not exactly a single ideal shade like there is ‘pigeon’s blood’ for rubies, there is ‘royal blue’, which is a rich, deep and highly saturated blue most often associated with Burmese sapphires. There is also a softer ‘cornflower’ blue, named after the flower of the same name, which is more associated with Sri Lankan (Ceylon) stones, and finally, ‘padparascha’ - an orangey pink hue, like a peachy sunset, which commands its own price premium.



Sapphire is found in a number of locations worldwide, and among the precious stones, sapphire has the most complex hierarchy of historic sources. Also, unlike ruby and emerald, its most expensive source is actually one of its least productive.

Kashmir: This mountainous region to the northeast of India, bordering Pakistan, yielded a deposit of particularly beautiful sapphires in the late 19th century, which was discovered after a landslide. It wasn’t long until the deposit was mostly mined out, and while small deposits of sapphires are still occasionally discovered there, nothing has beaten that initial discovery. Kashmir sapphires at their best are an unequalled pure, mid blue of very strong saturation, often with a sea-green secondary hue visible from some angles. They’re also much loved for their diffuse inclusions, which give them a distinctly velvety, sleepy look. Due to their rarity and beauty, it’s no surprise that Kashmir sapphires are the most expensive sapphires per carat.

A beautiful unheated Burmese sapphire in the Antique Ring Boutique collection, in an attractive, saturated blue.


Myanmar: Burmese sapphires vie with Kashmir sapphires for the coveted top spot in terms of value. In recent years this has been a particularly close race, as prominent Burmese stones have wowed their audiences at auction, with their excellent clarity and their fine shade of deep, rich blue, the best of which is known as ‘royal blue’.

An unheated Sri Lankan sapphire ring in the Antique Ring Boutique collection, showing its softer, lighter blue.


Sri Lanka: Probably the most varied, Sri Lanka produces a very significant number of sapphires every year. It’s also the most historic source of sapphires, with production going back millennia. Blue sapphires from this locality are most famous for their soft, slightly violet ‘cornflower’ blue, which is extremely attractive. At generally a much lower price point than their Burmese and Kashmiri counterparts, Sri Lankan sapphires can be excellent value for money, with a spectrum of beautiful colours for reasonable prices, yet from an extremely historically important source. The best Sri Lankan blues can rival Burmese sapphires, and the richer this blue the more expensive the stone will be. Sri Lanka also tends to be the best source of yellow and pink sapphires, as well as the orangey pink variety known as ‘padparascha’, which are also highly prized.

A very rare unheated teal sapphire from Montana, also in the Antique Ring Boutique collection.


Montana: This state of the USA yielded sapphires of its own in the late 19th century, which caught the eye of Tiffany’s head gemologist, George Frederick Kunz. The sapphires were relatively small, but in a beautiful spectrum of colours, including wonderful sky blues and distinctive teals, which has attracted a dedicated following of collectors, particularly as they’re very rare on the market outside the USA.

Madagascar: Increasingly recognised as a source of superb sapphires, Madagascar produces stones that, at their best, can rival the blues of Burmese and even Kashmir sapphires. Madagascar sapphires are not particularly common, but as with most newer deposits of high quality stones, there’s a high chance they could climb in value as they become more established in the market.

Australia, Cambodia and Thailand: Collectively these sapphires are often referred to as ‘basaltic’ sapphires due to the nature of their mineral deposits. Their blues tend to have a greenish tint, and are commonly darker in tone, sometimes appearing almost black, particularly with Australian examples. Basaltic sapphires on average are the lowest in terms of price per carat, but unheated examples of very attractive colour and good clarity do exist and can be superb value for money as a result.



The vast majority of sapphires on the market are heat treated. For sapphires in particular, there’s a good reason for this - they commonly have a inclusion called ‘silk’, which is an intricate network of needle-like crystals of titanium oxide. When these dissolve in heat, the titanium turns the stone a rich, vibrant blue, boosting its colour and clarity at the same time. For particularly included sapphires with little body colour, sometimes heat treatment is therefore the best option. While heat treatment is very common and accepted in the industry, heated sapphires are a fraction of the value of their rarer, higher quality, unheated counterparts, so it’s very important that this information regarding treatment is disclosed when the sapphire is sold. Always ask if you’re in doubt.


Emeralds are a variety of the mineral beryl, which is a crystal of beryllium aluminium cyclosilicate. Emeralds owe their green to the same element which creates the red in rubies - chromium. They are more brittle than other stones, and are almost always included, but they more than make up for this with their unrivalled colour.



Emeralds have no equivalent to ‘pigeon’s blood red’ or ‘royal blue’ - one colour to which all others are held. Therefore, the ideal colour of emeralds doesn’t really have an agreed upon description, apart from the obvious ‘emerald green’, which isn’t very helpful.

However, the same rules apply - the most expensive emeralds have a relatively pure green hue, perhaps leaning slightly more towards blue than yellow, of perhaps a slightly dark tone, but not too dark, and very strong saturation. If you’re having trouble visualising what this might look like, a useful reference (at least in the UK) is the colour of green Fairy Liquid!

Lighter emeralds can also be very attractive, and the light bluish, minty green varieties are increasingly finding popularity among jewellery designers, particularly with jewellers like Cartier.



Clarity is an extremely important issue for emeralds. Almost all emeralds are naturally included, and this is widely accepted, and in some instances even celebrated. The pattern of inclusions inside each emerald is affectionately known as its ‘jardin’, or ‘garden’, and those inclusions are like a unique fingerprint for each stone, telling you a lot about how the emerald was formed.

Nevertheless, no matter how interesting, varied and wonderful these inclusions are (particularly under microscope), too many inclusions can become an issue. While you can’t expect an emerald to be completely free from inclusions, you still want to be able to see into the stone. If the inclusions severely impact the way light travels through the stone, or are completely diffuse throughout the stone, then it’s going to have a negative impact on its appearance and durability, and therefore its value.

At the other end of the scale, emeralds which are completely free from inclusions do exist, but they are exceptionally rare and come at a significant premium, particularly when the stone is of good colour. You’ll also need to be sure about the level of clarity enhancement, so let’s talk about that now.

A lovely Colombian emerald, of good transparency, with a laboratory certificate showing only minor clarity enhancement.



As almost all emeralds are included, almost all emeralds will have had some form of clarity enhancement to help keep them looking their best. To improve clarity, emeralds are never heated, like sapphires and rubies - instead they are oiled. This is a very traditional practice, widely accepted in the industry, where natural oils (usually cedar oil) are soaked into the emerald, getting into the stone through surface cracks, and concealing the inclusions within. This is also reversible. However, it is useful to know how much oil is in the stone, as it will be an important indication of how included and potentially how fragile the stone really is. The cleaner the crystal, the less oil it will require, and the less oil it has, the more valuable it will be. The extent of clarity enhancement is graded on a scale like this: ‘none’, ‘insignificant’, ‘minor’, ‘moderate’ and ‘significant’.

There’s also a newer type of clarity enhancement using artificial resin - it works very well, but it can have a slightly negative impact on the value of the emerald, as unlike oil, it’s irreversible.

Finally, that tiny proportion of emeralds lucky enough to have no inclusions and no clarity enhancement command a hefty price premium, so make sure the ‘no oil’ certificate is up to date!



With emeralds, there’s one major origin, Colombia, which is the most highly valued, and the rest fall behind.

Colombia: This is the major source of the world’s emeralds, and has been for centuries. Colombian emeralds are formed differently in the earth to all other deposits, and at their best, they are the best in the world. Colombian emeralds are divided among different regional mines, most notably the Muzo and Chivor mines, but unless it’s a particularly large and important stone, it’s not really essential information, and in any case, each location produces excellent stones. Colombian emeralds vary in quality like emeralds from any other location, but like for like, they will generally be more expensive than emeralds from elsewhere.

Zambia: Increasingly a major source of the world’s emeralds. Deposits in Zambia were first discovered in the late 1920s, but has only been commercially mined since the 1970s. The Zambian mines can produce emeralds of very good colour and clarity, close to Colombian emeralds.

Russia: A source of emeralds in the Ural mountains, some of superb quality, which have been mined since the mid 19th century. Russian emeralds were historically coveted and quite rare, so the occasional Russian emerald of good quality can also command relatively high prices.

There are other deposits of emeralds including Brazil, Afghanistan, Pakistan, Zimbabwe and Ethiopia, all of which can also produce very good quality stones, but are generally lesser known.

In Conclusion...

We told you at the beginning it was going to be a complicated answer, but in any case we hope you find this buying guide useful.

To reiterate, by all means look at at the certificates, ask us about origin and treatment and anything else that’s on your mind, but ultimately it’s about the beauty and quality of the stone itself, how much you like the ring it’s set into, and, of course, how good it makes you feel. Luckily, there’s something beautiful out there for almost any budget, so don’t lose heart.

Finally, it’s easy to get lost in the minutiae of origin and treatment, but you’re not on your own. We’re always here to help, and if you have any questions about any of our stones, then we’re only an email, phone call or Instagram message away.

Good luck, and happy hunting!