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Sapphire: the September birthstone

Three loose blue sapphires

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In recent years, we've seen an increasing number of customers choosing sapphire engagement rings, a trend which accelerated after Prince William proposed to the Princess of Wales in 2011 with the sapphire ring he inherited from his mother, Princess Diana.

Sapphire is the September birthstone, making it an ideal choice if you or your partner have a September birthday, but there are also many other good reasons to choose a sapphire! In this article, we'll explore the appearance and characteristics of sapphires, their history and meaning, and how to care for them, and we'll answer the most frequently asked questions about this beautiful gemstone.

Appearance and characteristics of sapphires

Formed from a mineral called corundum (an aluminium oxide, Al2O3), sapphire is a very hard gemstone (only diamond is harder), scoring nine on the Mohs scale. This makes it well suited to withstand the wear and tear that engagement rings are subjected to. 

As well as their natural beauty and durability, part of the popularity of the September gemstone might also be explained by the fact that sapphires tend to be priced attractively compared to the other popular engagement ring gemstones — diamonds, emeralds and rubies.

However, unlike diamonds, it is relatively unusual for sapphires to be certified, and even certified sapphires are not graded against universally accepted criteria for colour, clarity and cut in the way that diamonds are. For this reason, it's worth spending a little time learning about the characteristics of sapphires to help you choose the best sapphire for you.

Sapphire size is measured in terms of carat weight

Like all gemstones, the size of a sapphire is expressed in terms of its carat weight, with 1 carat equal to 0.2 grams. It's worth bearing in mind that sapphire is about 50% more dense than diamond, so a sapphire will be a little smaller than a diamond of the same weight.

It's not always the case that 'bigger equals better', as a very large sapphire could be impractical for an engagement ring that will be worn daily. Cost is also a consideration, as the value of a sapphire will tend to increase exponentially with size. In other words, if you double the size of a sapphire, then the value of the stone will more than double.

Sapphires come in many colours – not just blue!

Sapphires are commonly thought of as blue gemstones, but they also come in pinks, yellows, purples, oranges and greens. Generally, when used on its own, the term sapphire is used to mean blue sapphire, with all colours being referred to collectively as fancy sapphires.

The different colours are caused by trace amounts of other minerals in the corundum, typically some mix of iron, titanium, and chromium. For example, blue sapphires contain trace amounts of iron and titanium; pink sapphires contain trace amounts of chromium; and yellow sapphires contain trace amounts of iron.

loose sapphires
Sapphires come in a wonderful array of colours

Any given colour of sapphire is further defined in terms of its hue, saturation and tone: 

  • Hue refers to the shade of blue, pink, yellow, etc. For example, it might be blue with a faint hint of violet, or pink with a hint of orange.
  • Saturation refers to how intense the colour is; generally, the more intense the better. 
  • Tone refers to how light or dark the stone is, with a medium tone (not too dark) generally considered the best.

Many clients prefer a rich royal blue or peacock blue shade that looks good under various light sources. In bright daylight, pale stones can look 'washed out', while dark sapphires perform less well under weaker light.

Rubies are red sapphires

Most people outside the jewellery industry are unaware that ruby is the name given to red sapphires, with the colour caused by trace amounts of chromium. And, even within the trade, there is a lack of consensus on quite where the boundary lies between pink sapphires and rubies:

  • the Gemological Institute of America (GIA) recognises only corundum with a dominant red hue as ruby;
  • the International Colored Gemstone Association (ICA) considers any red corundum to be ruby, regardless of colour depth or intensity; while
  • the International Gem Society (IGS) recognises both pinkish rubies and pink sapphires.

Padparadschas are orange-pink sapphires

Loose padparadscha sapphires
Loose padparadscha sapphires

Another unique fancy-coloured sapphire with its own name is the padparadscha, which means 'lotus flower' in the Sinhalese language of Sri Lanka, where it was first found. A beautiful orange-pink colour, true padparadschas are extremely rare and trade at a significant price premium to all other sapphire colours.

Colour-change sapphires change their appearance under different lighting conditions

Colour-change sapphires are very unusual corundum gems that change colour under different lighting. Typically, under daylight or daylight equivalent electric lighting, they are blue to violet in colour and change to violetish - to reddish-purple under incandescent light. The strength of the stone's colour change is the most important quality factor affecting its value, with the colour change being described as weak, moderate, or strong.

Many sapphires exhibit some colour zoning

Loose sapphire with visible colour zoning
Sapphire with colour zoning

Ideally, the colour within a sapphire would be completely evenly distributed, but it is common for this not to be the case, creating patches of light and dark. This is known as 'zoning' and can give sapphires a slightly stripy appearance, as shown in the stone above. Often sapphires are cut so that any zoning is not visible when the stone is viewed from above, which means that with an appropriate setting (such as a rub-over setting), the zoning will be invisible in the finished jewellery.

Most sapphires have some inclusions

Sapphires are defined as 'Type 2' gemstones by the Gemological Institute of America (GIA). This means it's very rare to find sapphires that are entirely free of natural blemishes or 'inclusions'.

Generally, inclusions make a stone less valuable. Still, for most clients, the important thing is how the stone looks to their naked eye, and if a sapphire has one or two very small inclusions, this is often considered acceptable. If you're looking for a flawless sapphire, be aware that these can be extremely expensive!

Pale blue sapphire with visible inclusions
Pale blue sapphire with visible inclusions

Several types of inclusions are found in sapphires, including long thin mineral inclusions called needles, mineral crystals, and partially-healed breaks that look like fingerprints.

In some rare cases, inclusions can increase a sapphire's value. For example, some of the most valuable Kashmir sapphires contain fine needle inclusions of rutile (titanium dioxide, TiO2) called 'silk' that scatter light, causing a beautiful velvety appearance without reducing transparency.

Needle-like inclusions are responsible for star sapphires

Star Sapphire
Star sapphire with six rays
(courtesy of Wikimedia Commons)

Star sapphires display an optical effect known as asterism, caused by reflections from tiny needle inclusions oriented in several specific directions. The stars usually have two or three intersecting bands, resulting in four or six rays.

star sapphire bespoke engagement ring
Bespoke star sapphire ring by Ingle & Rhode

Usually, rutile inclusions are responsible for the bright white star patterns, but it is also possible for a sapphire to have hematite inclusions (an iron oxide, Fe2O3) which produce a darker star pattern. And in extremely rare cases, some sapphires contain both rutile and hematite and exhibit both stars at once, creating a twelve-pointed star rather than the usual six.

Oval cut and cushion cut sapphires tend to offer the best value

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Cushion cut royal blue sapphire from Sri Lanka

A gem cutter's job is to maintain as much weight as possible while achieving the best colour, clarity and proportions. The facets should be sharply defined with a smooth finish. Sapphires can often be left quite deep relative to their total weight. It's worth checking how well a sapphire has been finished, as not all cutters are equally skilful or careful.

Rough sapphire crystals
Rough sapphire crystals (clockwise from the top: dark blue, light blue, yellow, orange and padparadscha)

Most rough sapphire crystals have a slightly elongated shape, which means that cutting to oval or rectangular cushion shapes will tend to preserve the most weight. As a result, there is usually a good selection of top-quality stones to choose from in these shapes. While it is possible to source other shapes, there is less choice, and they tend to trade at a premium price.

Look out for undisclosed sapphires treatments

Unless a supplier tells you otherwise, you should assume that a sapphire has been heated. This permanent treatment is so common and well-established within the industry that disclosing it is not generally thought necessary. This is a centuries-old process to improve a sapphire's colour and clarity, leaving it in a stable state that won't alter over time.

A few sapphires are naturally so good that the supplier will decide not to have them heated. Often these stones will be sent to a laboratory for certification and supplied with paperwork to confirm 'no evidence of thermal enhancement'. As you might expect, certified unheated sapphires tend to trade at a significant premium.

There are two particular treatments that you should be wary of. The first is diffusion, which involves heating sapphires alongside materials like titanium or beryllium, which diffuse into the crystal. The result is a layer of strong colour near the surface, which doesn't permeate through the stone. Subsequent chipping or recutting will reveal the true colour within. The second is fracture filling, where inclusions are filled with resin or lead glass to improve a sapphire's clarity. At first glance, the stone might appear better looking, but the more this is done, the weaker the stone becomes.

Fracture-filled and diffused sapphires are not valuable and should only be sold with full disclosure of these treatments. If you are in doubt, ask to have a sapphire examined by an independent gemologist before making a decision.

The history and meaning of the September birthstone

The September birthstone has long been associated with royalty and romance. Sapphires feature heavily in the British Crown Jewels, and their association with romance was reinforced when Prince Charles famously gave a blue sapphire engagement ring to Princess Diana in 1981 (the same ring that Prince William gave to Princess Catherine in 2011).

The name of the September birthstone comes from the ancient Greek word "sappheiros", although it is now thought that the ancient Greeks used this word to refer to a different blue gemstone: lapis lazuli. 

Loose lapis lazuli
Lapis lazuli - the blue gemstone that the ancient Greeks called sappheiros

According to Greek mythology, Helen of Troy was said to have owned a large star sapphire. The ancient Greeks also associated sapphires with the god Apollo and wore sapphires when seeking answers from the Oracle at the Temple of Apollo at Delphi. They also believed that wearing sapphires protected them from harm, as did Arabian kings many years later.

Ancient Persians believed that the Earth was supported on a vast pedestal made of sapphire, whose reflection caused the sky to be blue, while in the Hindu faith, the Kalpavriksha is a divine tree whose roots are said to be made of sapphires.

Some Buddhists believed that sapphires have a calming effect, facilitating devotion to prayer and meditation and helping to bring spiritual enlightenment. At the same time, in the Jewish, Christian and Islamic faiths, the Ten Commandments were said to have been engraved on tablets of sapphire (though historians now believe the old testament may be referencing lapis lazuli). King Solomon was also said to have had a ring (the 'seal' of King Solomon) carved from sapphire.

Indeed, sapphires have been key symbols in the Christian religion for many years. Early Christian kings harnessed sapphire's powers of protection in ecclesiastical rings, and from the middle ages, Christian clergy wore blue sapphires to symbolise Heaven and purity, as well as for their healing properties. At various times, sapphires were believed to alleviate everything from hiccups and nosebleeds to mental illness, blindness and cancer.

How to care for a sapphire

Sapphires are durable gemstones that stand up well to normal wear and tear. That said, they are not indestructible, so it is always wise to remove and safely store your sapphire engagement ring if you're exercising or performing manual tasks.

You can clean your sapphire at home with warm water and a splash of detergent, using a soft toothbrush, but avoid using any strong chemicals or abrasives that might leave a residue or damage the surface of your sapphire.

If you damage your sapphire, you should take it to your jeweller for a professional repair. Minor chips and scratches can often be polished out with very little loss of carat weight, but larger chips may result in the stone needing to be recut.


Where do sapphires come from?

Historically, the finest blue sapphires came from the Kashmir region of India between the late 19th and early 20th centuries, before Sri Lanka (with so-called Ceylon sapphires) replaced Kashmir as the primary source of fine sapphires. More recently, Madagascar has overtaken Sri Lanka in sapphire gemstone production, and sapphires are also mined in Tanzania, Malawi, Myanmar, Australia and the US.

When did the sapphires become popular?

Sapphires have been prized for thousands of years across many cultures and faiths, but their popularity has increased notably in the two hundred years since the industrial revolution two hundred years ago, with the growing numbers of affluent consumers in advanced economies. This trend only accelerated after Prince William proposed to the Princess of Wales in 2011 with the sapphire ring he inherited from his mother, Princess Diana.

Can sapphires be lab-grown?

Yes, they can. A French chemist, Auguste Verneuil, developed a process to make synthetic sapphire in 1902, and it has been readily available ever since then. Lab-grown sapphire is widely used for industrial applications, but gem-quality lab-grown sapphire can also be used to make jewellery. As with diamonds, if a sapphire is lab-grown, its status should always be disclosed, and any attempt to pass off lab-grown sapphire as natural should be treated as fraud.

Are sapphires more expensive than diamonds?

Generally speaking, no, but as with most things, it depends. The price of a diamond ranges massively depending on the size and quality of the stone in question, and the same is true of a sapphire. The highest price-per-carat for the September gemstone was set by a Kashmir sapphire, which sold at auction in October 2015 for $242,000 per carat (and more than $6.74 million in total). That is MUCH more than most diamonds are worth, but that said, the world's most valuable diamonds are worth hundreds of millions, if not billions of dollars!

Where can I source an ethical sapphire?

Like all precious metals and gems, the sapphire supply chain is often blighted by environmental damage and human exploitation. Sapphire mining can have a terrible impact on the local environment, working conditions can be hazardous, and child labour is not uncommon. The "sapphire rush" in Madagascar in recent years has seen significant environmental damage. For this reason, it is very important when sourcing a sapphire that your jeweller can tell you exactly where the stone came from and where it was cut and polished. If your jeweller cannot answer these questions, then they cannot provide you with any meaningful assurances.

At Ingle & Rhode, we source only traceable sapphires that have been produced in a socially and environmentally responsible way. The vast majority of our sapphires come from small-scale cooperatives in Sri Lanka, where there is no child labour, the rewards are shared fairly between the miners and the landowner, and the land is restored once the mining is finished. And all our gemstones are cut and polished by adults working for fair pay in good conditions.


Sapphire, the September birthstone, is a beautiful gem found in many colours and has been prized for thousands of years in many different cultures and faiths.

A form of the mineral corundum, it scores 9 on the Mohs scale, making it second only to diamond in terms of hardness, and therefore well suited to use in jewellery.

In addition to colour, it is important to consider the clarity and cut of a sapphire and to look out for any potential treatments that the gemstone may have been subjected to.

Most sapphires nowadays come from Sri Lanka and Madagascar, but it is important that your jeweller can tell you about where their gems come from and how they are produced because, without that traceability, you cannot be sure that your sapphire was ethically sourced.

David Rhode
Together with Tim Ingle, David created Ingle & Rhode to offer a better alternative to the traditional luxury brands. Since 2007, we’ve provided our customers with genuinely ethical engagement rings, wedding rings and fine jewellery – free from conflict diamonds, dirty gold and child labour. With more than 16 years experience in the jewellery industry, David has deep expertise in diamonds, gemstones and jewellery design and manufacturing.