How To Choose a Sapphire

Ever since Prince William proposed to Kate Middleton with a sapphire engagement ring, we have seen a marked rise in the number of clients considering these beautiful gemstones to mark their own engagements.

Sapphires are particularly well suited for setting in engagement rings, since not only are they majestic stones, they are also fairly hard and so stand up well to everyday wear and tear. Furthermore, they are attractively priced compared to diamonds, rubies and emeralds, making this gemstone a good option if you want a larger ring.

Sapphires work beautifully alongside diamonds in vintage or art deco designs, but unlike diamonds, sapphires aren’t graded according to the ‘4 Cs’: a universally accepted set of guidelines for assessing the value of a diamond. As a result, choosing a sapphire is less a matter of looking at a third-party certificate, and more about personal judgement. So what factors should a prospective buyer have in mind?

Size
There is no ideal size for a sapphire, and while many clients lean towards the old adage ‘the bigger, the better’, just as many are keen not to look overly ostentatious. You should also be aware that most women will want to wear their engagement ring every day, but a very large sapphire could make this impractical. Similarly, consider whether the sapphire will be set on its own, or complemented with other stones. For example if a sapphire is to be surrounded by a halo of small diamonds, these can add considerably to the overall size of the setting.

Of course, cost is also a consideration, and all else being equal, the value of a sapphire increases with size. But not only does it increase, it increases exponentially. That’s to say, if you could double the size of a sapphire, the value of the gem would more than double! This is driven by supply and demand. Larger gems are more scarce than smaller gems (so supply decreases as size increases), but given a free choice most people would choose a larger gem over a smaller one (so demand increases with size).

Colour
Sapphires are most commonly thought of as blue gems, but in reality they are found in a wide range of colours, including yellows, pinks, oranges, greens and purples.

Like size, the ideal colour for a sapphire is subjective, but most clients favour a rich royal blue. Pale stones risk looking ‘washed out’ in bright light, while very dark sapphires can appear inky black as soon as the light starts to fade. Royal blue tends to look good under a range of different light sources, and its popularity is reflected in its pricing.

One thing to look out for and avoid is ‘zoning’ in a stone’s colour. If the colour isn’t distributed evenly throughout the crystal, then the sapphire can appear almost translucent from certain angles.

Clarity
Most sapphires contain small blemishes or ‘inclusions’. A small minority are entirely clean, even when viewed under the 10x magnification of a jeweller’s loupe, and these stones trade at a premium. For most clients, this level of clarity represents an unnecessary expense – what really matters is how the sapphire appears to the naked eye, and many stones include small inclusions while remaining ‘eye clean’. If a sapphire does have inclusions that are visible to the naked eye then this is often a problem, but not always – some blemishes can be severely disfiguring, while others are hardly noticeable.

Shape
Sapphires are found as rough crystals that are formed naturally under the earth’s crust. A cutter’s job is to facet and polish the crystal into its final shape, and to minimise wastage while they are doing this. Because rough sapphires tend to have an elongated shape, oval cuts and rectangular cushion cuts tend to preserve most of the rough crystal, while rounds, marquise and octagonal shapes are more wasteful. For this reason, while there should always be a good selection of top-quality ovals and rectangular cushions to choose from, other shapes can be harder to source and tend to be priced at a premium

Cut
Not every gem cutter works with the same degree of skill and care. A well cut sapphire has sharply defined facets, finished with a smooth and even polish. Unlike diamonds, which are cut to maximise sparkle, sapphires are primarily cut for colour. This allows for a degree of flexibility regarding the stone’s proportions. Sapphires are often quite deep relative to their overall size, as this helps to preserve the colour of the rough crystal.

Treatment
There are a number of ways in which sapphires can be treated to enhance their appearance. In principle there is nothing wrong with purchasing a treated stone, so long as the nature of any treatment has been fully disclosed; the buyer is aware of the potential risks associated with the treatment; and the gem is appropriately priced.

Unless you’re told otherwise, you should assume a sapphire has been heated. The vast majority of sapphires on the market are treated in this way to improve their colour and clarity. This is a centuries-old technique, and is completely stable, meaning that the appearance of the sapphire will not deteriorate or change over time. For this reason, heated sapphires retain their value.

A small minority of sapphires have such good colour and clarity that there is no need to heat them. Unheated sapphires tend to come with a certificate from a gemological laboratory, and can trade at a significant premium.

Heat treatment is in sharp distinction to ‘diffusion’, a group of techniques that involve heating sapphires near to their melting point with other chemicals (such as beryllium or titanium). The chemicals diffuse into the sapphire, creating a layer of rich colour near the surface of an otherwise weak stone. If the sapphire is later chipped or re-polished, its poor natural colour will be revealed. Diffused stones are almost worthless.

Another treatment to be wary of is fracture filling. Resin or high-lead content glass are used to fill cavities or inclusions in the stone to improve its clarity. This treatment can make low-quality sapphires seem superficially more attractive, but in extreme cases the stone is more or less held together only by the filling – both vulnerable to damage, and nearly worthless.

In summary then, clients should consider whether the size and shape of a sapphire will suit the design they have in mind for their engagement ring; and whether the quality of the stone, in terms of its colour, clarity and cut, meets with their requirements. Finally, they should seek confirmation, ideally in writing as to what treatments the sapphire may have received. Having considered all of these issues, they will then be in a position to make an informed decision when comparing different sapphires.

This article is by David Rhode, of ethical jeweller Ingle & Rhode.
Dark blue sapphire ring photo from Shutterstock
Sapphires photo from Shutterstock
Gold Sapphire ring photo from Shutterstock

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